10-Q

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-Q

☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended March 31, 2024

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from _____ to _____

		I.R.S. Employer
Commission File Number	Exact name of registrant as specified in its charter	Identification Number
001-3375	DOMINION ENERGY SOUTH CAROLINA, INC.	57-0248695
	south carolina
	(State or other jurisdiction of incorporation or organization)
	220 OPERATION WAY
	CAYCE, South Carolina	29033
	(Address of principal executive offices)	(Zip Code)
	(804) 819-2284
	(Registrants’ telephone number)

Securities registered pursuant to Section 12(b) of the Act:

None

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “non-accelerated filer,” “smaller reporting company” and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer	☐	Accelerated filer	☐	Emerging growth company	☐
Non-accelerated filer	☒	Smaller reporting company	☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

Indicate the number of shares outstanding of each of the issuer’s classes of common stock, as of the latest practicable date. At April 26, 2024, Dominion Energy South Carolina, Inc. had outstanding 40,296,147 shares of common stock, all of which were held by SCANA Corporation, a wholly-owned subsidiary of Dominion Energy, Inc.

Dominion Energy South Carolina, Inc. meets the conditions set forth in General Instruction H(1)(a) and (b) of Form 10-Q and is filing this Form 10-Q under the reduced disclosure format.

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TABLE OF CONTENTS

		Page
	Glossary of Terms	3
PART I. FINANCIAL INFORMATION
Item 1.	Financial Statements	5
Item 2.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	26
Item 4.	Controls and Procedures	28
PART II. OTHER INFORMATION
Item 1.	Legal Proceedings	29
Item 1A.	Risk Factors	29
Item 5.	Other Information	29
Item 6.	Exhibits	30

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GLOSSARY OF TERMS

The following abbreviations or acronyms used in this Form 10-Q are defined below:

Abbreviation or Acronym	Definition
2017 Tax Reform Act	An Act to Provide for Reconciliation Pursuant to Titles II and V of the Concurrent Resolution on the Budget for Fiscal Year 2018 (previously known as The Tax Cuts and Jobs Act) enacted on December 22, 2017
ACE Rule	Affordable Clean Energy Rule
AFUDC	Allowance for funds used during construction
AOCI	Accumulated other comprehensive income (loss)
ARO	Asset retirement obligation
BACT	Best available control technology
CAA	Clean Air Act
CCR	Coal combustion residual
CEO	Chief Executive Officer
CERCLA	Comprehensive Environmental Response, Compensation and Liability Act of 1980, also known as Superfund
CFO	Chief Financial Officer
CO2	Carbon dioxide
CPCN	Certificate of Public Convenience and Necessity
CUA	Capacity Use Area
CWA	Clean Water Act
DES	Dominion Energy Services, Inc.
DESC	The legal entity, Dominion Energy South Carolina, Inc., one or more of its consolidated entities or operating segment, or the entirety of Dominion Energy South Carolina, Inc. and its consolidated entities
Dominion Energy	The legal entity, Dominion Energy, Inc., one or more of its consolidated subsidiaries (other than DESC) or operating segments, or the entirety of Dominion Energy, Inc. and its consolidated subsidiaries
Dominion Energy South Carolina	Dominion Energy South Carolina operating segment
DSM	Demand-side management
ELG Rule	Effluent limitations guidelines for the steam electric power generating category
EPA	U.S. Environmental Protection Agency
FERC	Federal Energy Regulatory Commission
Fuel Company	South Carolina Fuel Company, Inc.
GAAP	U.S. generally accepted accounting principles
GENCO	South Carolina Generating Company, Inc.
GHG	Greenhouse gas
kV	Kilovolt
MD&A	Management’s Discussion and Analysis of Financial Condition and Results of Operations
MGD	Million gallons per day
MWh	Megawatt hour
NND Project	V. C. Summer Units 2 and 3 nuclear development project under which DESC and Santee Cooper undertook to construct two Westinghouse AP1000 Advanced Passive Safety nuclear units in Jenkinsville, South Carolina
NOx	Nitrogen oxide
Order 1000	Order issued by FERC adopting requirements for electric transmission planning, cost allocation and development
PSD	Prevention of significant deterioration
Questar Gas	Questar Gas Company, a wholly-owned subsidiary of Dominion Energy
ROE	Return on equity

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Abbreviation or Acronym	Definition
Santee Cooper	South Carolina Public Service Authority
SCANA	The legal entity, SCANA Corporation, one or more of its consolidated subsidiaries (other than DESC) or the entirety of SCANA Corporation and its consolidated subsidiaries
SCANA Combination	Dominion Energy’s acquisition of SCANA completed on January 1, 2019 pursuant to the terms of the SCANA Merger Agreement
SCANA Merger Agreement	Agreement and plan of merger entered on January 2, 2018 between Dominion Energy and SCANA
SCANA Merger Approval Order	Final order issued by the South Carolina Commission on December 21, 2018 setting forth its approval of the SCANA Combination
SCDHEC	South Carolina Department of Health and Environmental Control
SCDOR	South Carolina Department of Revenue
SEC	U.S. Securities and Exchange Commission
SO2	Sulfur dioxide
South Carolina Commission	Public Service Commission of South Carolina
Summer	V. C. Summer nuclear power station
Toshiba	Toshiba Corporation, parent company of Westinghouse
Toshiba Settlement	Settlement Agreement dated as of July 27, 2017, by and among Toshiba, DESC and Santee Cooper
VIE	Variable interest entity
Virginia Power	The legal entity, Virginia Electric and Power Company, a wholly-owned subsidiary of Dominion Energy, one or more of its consolidated subsidiaries or operating segment, or the entirety of Virginia Electric and Power Company and its consolidated subsidiaries
Westinghouse	Westinghouse Electric Company LLC

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PART I. FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

Dominion Energy South Carolina, Inc.

Consolidated Balance Sheets

(Unaudited)

(millions)	March 31, 2024			December 31, 2023
ASSETS
Utility plant in service	$	15,570		$	15,500
Accumulated depreciation and amortization		(5,591	)		(5,557	)
Construction work in progress		702			606
Nuclear fuel, net of accumulated amortization		226			229
Utility plant, net ($788 and $773 related to VIEs)		10,907			10,778
Nonutility Property and Investments:
Nonutility property, net of accumulated depreciation		24			24
Assets held in trust, nuclear decommissioning		254			247
Nonutility property and investments, net		278			271
Current Assets:
Cash and cash equivalents		4			1
Receivables:
Customer, net of allowance for uncollectible accounts of $8 and $6		399			420
Affiliated and related party		3			4
Other		63			97
Inventories (at average cost):
Fuel		92			94
Gas stored		22			30
Materials and supplies		243			232
Prepayments		78			84
Regulatory assets		351			444
Other current assets(1)		30			23
Total current assets ($87 and $89 related to VIEs)		1,285			1,429
Deferred Debits and Other Assets:
Regulatory assets		3,094			3,107
Affiliated receivables		4			4
Other(1)		339			268
Total deferred debits and other assets ($26 and $26 related to VIEs)		3,437			3,379
Total assets	$	15,907		$	15,857

(1) See Note 12 for amounts attributable to affiliates.

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Balance Sheets—(Continued)

(Unaudited)

(millions)	March 31, 2024			December 31, 2023
CAPITALIZATION AND LIABILITIES
Common Stock - no par value, 40.3 million shares outstanding	$	4,088		$	4,088
Retained earnings		604			592
Accumulated other comprehensive loss		(1	)		(1	)
Total common equity		4,691			4,679
Noncontrolling interest		189			183
Total equity		4,880			4,862
Long-term debt, net		4,219			4,219
Finance leases		3			4
Total long-term debt		4,222			4,223
Total capitalization		9,102			9,085
Current Liabilities:
Short-term borrowings		210			254
Securities due within one year		3			3
Accounts payable		135			180
Affiliated and related party payables		1,013			740
Customer deposits and customer prepayments		71			75
Taxes accrued		71			248
Interest accrued		81			79
Regulatory liabilities		233			205
Other		133			166
Total current liabilities		1,950			1,950
Deferred Credits and Other Liabilities:
Deferred income taxes and investment tax credits		1,323			1,318
Asset retirement obligations		734			731
Pension and other postretirement benefits		114			115
Regulatory liabilities		2,598			2,579
Other		86			79
Total deferred credits and other liabilities		4,855			4,822
Commitments and Contingencies (see Note 10)
Total capitalization and liabilities	$	15,907		$	15,857

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Statements of Comprehensive Income

(Unaudited)

	Three Months Ended March 31,
(millions)	2024		2023
Operating Revenue(1)	$	775	$	759
Operating Expenses:
Fuel used in electric generation		145		150
Purchased power(1)		10		7
Gas purchased for resale		79		82
Other operations and maintenance		122		115
Other operations and maintenance - affiliated suppliers		41		41
Depreciation and amortization		136		129
Other taxes(1)		78		78
Total operating expenses		611		602
Operating income		164		157
Other income (expense), net		1		10
Interest charges, net of AFUDC of $4 and $4(1)		67		59
Income before income tax expense		98		108
Income tax expense		18		11
Net Income and Other Comprehensive Income		80		97
Comprehensive Income Attributable to Noncontrolling Interest		6		5
Comprehensive Income Available to Common Shareholder	$	74	$	92

(1) See Note 12 for amounts attributable to affiliates.

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Statements of Cash Flows

(Unaudited)

	Three Months Ended March 31,
(millions)	2024			2023
Operating Activities
Net income	$	80		$	97
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes, net		5			5
Depreciation and amortization		136			129
Amortization of nuclear fuel		9			9
Other adjustments		—			(7	)
Changes in certain assets and liabilities:
Receivables		45			91
Receivables - affiliated and related party		1			1
Inventories		(1	)		—
Prepayments		2			5
Regulatory assets		79			56
Regulatory liabilities		41			(122	)
Accounts payable		(18	)		(87	)
Accounts payable - affiliated and related party		43			11
Taxes accrued		(177	)		(165	)
Interest accrued		2			(7	)
Pension and other postretirement benefits		(1	)		—
Other assets and liabilities		(80	)		56
Net cash provided by operating activities		166			72
Investing Activities
Property additions and construction expenditures		(268	)		(283	)
Proceeds from investments and sales of assets		(13	)		(8	)
Purchase of investments		(5	)		(4	)
Other		—			1
Net cash used in investing activities		(286	)		(294	)
Financing Activities
Dividend to parent		(62	)		(50	)
Short-term borrowings, net		(44	)		28
Short-term borrowings - affiliated, net		230			235
Other		(1	)		1
Net cash provided by financing activities		123			214
Net increase (decrease) in cash, restricted cash and equivalents		3			(8	)
Cash, restricted cash and equivalents at beginning of period(1)		1			11
Cash, restricted cash and equivalents at end of period(1)	$	4		$	3
Supplemental Cash Flow Information
Significant noncash investing and financing activities:(2)
Accrued construction expenditures	$	56		$	54

(1)At March 31, 2024, December 31, 2023, March 31, 2023 and December 31, 2022 there were no restricted cash and equivalent balances.

(2)See Note 10 for noncash investing activities related to the transfer of property associated with the settlement of litigation.

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Consolidated Statements of Changes in Common Equity

(Unaudited)

	Common Stock
(millions)	Shares		Amount		Retained Earnings			AOCI			Noncontrolling Interest		Total Equity
December 31, 2022		40	$	4,088	$	418		$	(2	)	$	162	$	4,666
Total comprehensive income available to    common shareholder						92						5		97
Dividend to parent						(50	)							(50	)
March 31, 2023		40	$	4,088	$	460		$	(2	)	$	167	$	4,713
December 31, 2023		40	$	4,088	$	592		$	(1	)	$	183	$	4,862
Total comprehensive income available to    common shareholder						74						6		80
Dividend to parent						(62	)							(62	)
March 31, 2024		40	$	4,088	$	604		$	(1	)	$	189	$	4,880

See Notes to Consolidated Financial Statements.

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Dominion Energy South Carolina, Inc.

Notes to Consolidated Financial Statements

(Unaudited)

The following notes should be read in conjunction with the Notes to Consolidated Financial Statements appearing in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

These are interim financial statements and, due to the seasonality of DESC’s business and matters that may occur during the rest of the year, the amounts reported in the Consolidated Statements of Comprehensive Income are not necessarily indicative of amounts expected for the full year. In the opinion of management, the information furnished herein reflects all adjustments which are necessary for a fair statement of the results for the interim periods reported, and such adjustments are of a normal recurring nature unless otherwise noted. In addition, the preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amount of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Certain amounts in DESC’s 2023 Consolidated Financial Statements and Notes have been reclassified to conform to the 2024 presentation for comparative purposes; however, such reclassifications did not affect DESC’s net income and other comprehensive income, total assets, liabilities, equity or cash flows.

DESC is a wholly-owned subsidiary of SCANA, which is a wholly-owned subsidiary of Dominion Energy.

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Consolidation and Variable Interest Entities

DESC has determined that it has a controlling financial interest in each of GENCO and Fuel Company (which are considered to be VIEs) and, accordingly, DESC’s Consolidated Financial Statements include, after eliminating intercompany balances and transactions, the accounts of DESC, GENCO and Fuel Company. See Note 2 to the Consolidated Financial Statements included in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for a description of GENCO and Fuel Company.

DESC purchases shared services from DES, an affiliated VIE that provides accounting, legal, finance and certain administrative and technical services to all Dominion Energy subsidiaries, including DESC. DESC has determined that it is not the primary beneficiary of DES as it does not have either the power to direct the activities that most significantly impact its economic performance or an obligation to absorb losses and benefits which could be significant to it. See Note 12 for amounts attributable to affiliates.

Significant Accounting Policies

There have been no significant changes from Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023, except as follows.

New Accounting Standards

Climate-Related Disclosures

In March 2024, the SEC issued guidance for climate-related disclosures. The guidance requires disclosure of the financial statement impacts of severe weather events and other natural conditions, including amounts capitalized or expensed as well as any associated recoveries. In addition, the guidance requires disclosure of amounts related to renewable energy credits or carbon offsets if utilized as a material component of plans to achieve climate-related targets or goals. This guidance, which is currently subject to a stay issued by the SEC, would be effective for the fiscal year beginning January 1, 2025. DESC expects this guidance to only impact its disclosures with no impacts to its results of operations, cash flows or financial condition.

2. RATE AND OTHER REGULATORY MATTERS

Regulatory Matters Involving Potential Loss Contingencies

As a result of issues generated in the ordinary course of business, DESC is involved in various regulatory matters. Certain regulatory matters may ultimately result in a loss; however, as such matters are in an initial procedural phase, involve uncertainty as to the outcome of pending reviews or orders, and/or involve significant factual issues that need to be resolved, it is not possible for DESC to estimate a range of possible loss. For regulatory matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the regulatory process such that DESC is able to estimate a range of possible loss. For regulatory matters that DESC is able to reasonably estimate a range of possible losses, an

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estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. Any estimated range is based on currently available information, involves elements of judgment and significant uncertainties and may not represent DESC’s maximum possible loss exposure. The circumstances of such regulatory matters will change from time to time and actual results may vary significantly from the current estimate. For current matters not specifically reported below, management does not anticipate that the outcome from such matters would have a material effect on DESC’s financial position, liquidity or results of operations.

Other Regulatory Matters

Other than the following matters, there have been no significant developments regarding the pending regulatory matters disclosed in Note 3 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

Electric Base Rate Case

In March 2024, DESC filed its retail electric base rate case and schedules with the South Carolina Commission. DESC proposed a non-fuel, base rate increase of $295 million, partially offset by a net decrease in storm damage and DSM components of $4 million. If approved, the overall proposed rate increase of $291 million, or 12.59%, would be effective on and after the first billing cycle of September 2024. The base rate increase was proposed to recover the significant investment in assets and operating resources required to serve an expanding customer base, maintain the safety, reliability and efficiency of DESC’s system and meet increasingly stringent reliability, security and environmental requirements for the benefit of South Carolina customers. DESC presented an earned ROE of 4.32% based upon a fully-adjusted test period. The proposed rates would provide for an earned ROE of 10.60% compared to the currently authorized ROE of 9.50%. This matter is pending.

Electric – Cost of Fuel

DESC’s retail electric rates include a cost of fuel component approved by the South Carolina Commission which may be adjusted periodically to reflect changes in the price of fuel purchased by DESC. In February 2024, DESC filed with the South Carolina Commission a proposal to decrease the total fuel cost component of retail electric rates. DESC’s proposed adjustment is designed to recover DESC’s current base fuel costs, including its existing under-collected balance, over the 12-month period beginning with the first billing cycle of May 2024. In addition, DESC proposed an increase to its variable environmental and avoided capacity cost component. The net effect is a proposed annual decrease of $315 million. In March 2024, DESC, the South Carolina Office of Regulatory Staff and another party of record filed a settlement agreement with the South Carolina Commission for approval to make certain adjustments to the February 2024 filing that would result in a net annual decrease of $316 million. In April 2024, the South Carolina Commission voted to approve the settlement agreement, with rates effective May 2024.

Electric - Transmission Project

In March 2024, DESC filed an application with the South Carolina Commission requesting approval of a CPCN to construct and operate the Church Creek - Charleston Transmission Line, comprised of a 7 mile 230 kV transmission line and associated facilities in Charleston County, South Carolina with an estimated total project cost of $40 million. This matter is pending.

Electric – Other

DESC has approval for a DSM rider through which it recovers expenditures related to its DSM programs. In January 2024, DESC filed an application with the South Carolina Commission seeking approval to recover $47 million of costs and net lost revenues associated with these programs, along with an incentive to invest in such programs. DESC requested that rates be effective with the first billing cycle of May 2024. In April 2024, the South Carolina Commission approved the request, effective with the first billing cycle of May 2024.

DESC utilizes a pension costs rider approved by the South Carolina Commission which is designed to allow recovery of projected pension costs, including under-collected balances or net of over-collected balances, as applicable. The rider is typically reviewed for adjustment every 12 months with any resulting increase or decrease going into effect beginning with the first billing cycle in May. In February 2024, DESC requested that the South Carolina Commission approve an adjustment to this rider to increase annual revenue by $9 million. In April 2024, the South Carolina Commission approved the request.

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Regulatory Assets and Regulatory Liabilities

Rate-regulated utilities recognize in their financial statements certain revenues and expenses in different periods than do other enterprises. As a result, DESC has recorded regulatory assets and regulatory liabilities which are summarized in the following table. Except for NND Project costs and certain other unrecovered costs referenced herein, substantially all regulatory assets are either explicitly excluded from rate base or are effectively excluded from rate base due to their being offset by related liabilities.

	March 31,		December 31,
(millions)	2024		2023
Regulatory assets:
NND Project costs(1)	$	138	$	138
AROs(2)		38		44
Deferred employee benefit plan costs(3)		7		11
Other unrecovered plant(4)		19		19
DSM programs(5)		22		22
Cost of fuel and purchased gas under-collections(6)		71		154
Other		56		56
Regulatory assets - current		351		444
NND Project costs(1)		1,915		1,949
AROs(2)		382		379
Deferred employee benefit plan costs(3)		120		118
Interest rate hedges(7)		168		168
Other unrecovered plant(4)		70		66
DSM programs(5)		46		46
Environmental remediation costs(8)		33		34
Deferred storm damage costs(9)		39		40
Deferred transmission operating costs(10)		73		74
Derivatives(11)		99		103
Other(12)		149		130
Regulatory assets - noncurrent		3,094		3,107
Total regulatory assets	$	3,445	$	3,551
Regulatory liabilities:
Monetization of guaranty settlement(13)	$	67	$	67
Income taxes refundable through future rates(14)		37		37
Reserve for refunds to electric utility customers(15)		83		83
Derivatives(11)		15		12
Cost of fuel and purchased gas over-collections(6)		21		—
Other		10		6
Regulatory liabilities - current		233		205
Monetization of guaranty settlement(13)		619		635
Income taxes refundable through future rates(14)		830		839
Asset removal costs(16)		640		633
Reserve for refunds to electric utility customers(15)		212		237
Derivatives(11)		296		229
Other		1		6
Regulatory liabilities - noncurrent		2,598		2,579
Total regulatory liabilities	$	2,831	$	2,784

(1)Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

(2)Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years.

(3)Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. DESC expects to recover deferred pension costs through utility rates over periods through 2044. DESC expects to recover other deferred benefit costs through utility rates, primarily over average service periods of participating employees up to 11 years.

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(4)Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2033. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized over five years related to the transition or conversion from coal to gas fired generation at certain facilities.

(5)Represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

(6)Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

(7)Represents the changes in fair value and payments made or received upon settlement of certain interest rate derivatives designated as cash flow hedges. The amounts recorded are expected to be amortized to interest expense over the lives of the underlying debt through 2065.

(8)Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

(9)Represents storm restoration costs for which DESC expects to receive future recovery through customer rates over approximately 10 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and are earning a current return.

(10)Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects recovery from customers through future rates over approximately 42 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and earning a current return. See Note 12 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

(11)Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

(12)Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

(13)Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

(14)Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years). See Note 7 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for additional information.

(15)Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

(16)Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

Regulatory assets have been recorded based on the probability of their recovery. All regulatory assets represent incurred costs that may be deferred under GAAP for regulated operations. The South Carolina Commission or FERC has reviewed and approved through specific orders certain of the items shown as regulatory assets. In addition, regulatory assets include, but are not limited to, certain costs which have not been specifically approved for recovery by one of these regulatory agencies. While such costs are not currently being recovered, management believes that they would be allowable under existing rate-making concepts embodied in rate orders or applicable state law and expects to recover these costs through rates in future periods.

3. REVENUE RECOGNITION

DESC has disaggregated operating revenues by customer class as follows:

Three Months Ended March 31,	2024				2023
(millions)	Electric		Gas		Electric		Gas
Customer class:
Residential	$	283	$	117	$	262	$	109
Commercial		188		41		187		42
Industrial		87		18		91		22
Other		28		6		36		4
Revenues from contracts with customers		586		182		576		177
Other revenues		7		—		6		—
Total Operating Revenues	$	593	$	182	$	582	$	177

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Contract liabilities represent the obligation to transfer goods or services to a customer for which consideration has already been received from the customer. DESC had contract liability balances of $6 million and $7 million at March 31, 2024 and December 31, 2023, respectively. During the three months ended March 31, 2024 and 2023, DESC recognized revenue of $3 million and $7 million, respectively, from the beginning contract liability balances as DESC fulfilled its obligations to provide service to its customers. Contract liabilities are recorded in customer deposits and customer prepayments in the Consolidated Balance Sheets.

Balances and activity related to contract costs deferred as regulatory assets were as follows:

	Regulatory Assets
(millions)	March 31, 2024		December 31, 2023
Beginning balance	$	11	$	9
Additional costs		—		3
Amortization		—		(1	)
Ending balance	$	11	$	11

4. EQUITY

For all periods presented, DESC’s authorized shares of common stock, no par value, were 50 million, of which 40.3 million were issued and outstanding, and DESC’s authorized shares of preferred stock, no par value, were 20 million, of which 1,000 shares were issued and outstanding. All outstanding shares of common and preferred stock are held by SCANA.

There have been no material changes to the dividend restrictions affecting DESC described in Note 5 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

5. LONG-TERM AND SHORT-TERM DEBT

DESC’s short-term financing is supported through its access as co-borrower to Dominion Energy’s $6.0 billion joint revolving credit facility, which can be used for working capital, as support for the combined commercial paper programs of DESC, Dominion Energy, Virginia Power and Questar Gas, and for other general corporate purposes. Other than the items discussed below, there have been no significant changes from Note 6 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

At March 31, 2024, DESC’s share of commercial paper and letters of credit outstanding under its joint credit facility with Dominion Energy, was as follows:

(millions)	Maximum Facility Sub-Limit		Outstanding Commercial Paper		Outstanding Letters of Credit
Joint revolving credit facility(1)	$	1,000	$	210	$	—

(1)A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2024, the sub-limit for DESC was $500 million. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.

In 2023, FERC granted DESC authority through March 2025 to issue short-term indebtedness (pursuant to Section 204 of the Federal Power Act) in amounts not to exceed $2.2 billion outstanding with maturity dates of one year or less. At March 31, 2024, DESC had issued $210 million in commercial paper under its joint credit facility with Dominion Energy as disclosed above and had drawn on $371 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization. In addition, in 2023, FERC granted GENCO authority through March 2025 to issue short-term indebtedness not to exceed $200 million outstanding with maturity dates of one year or less. At March 31, 2024, GENCO had drawn on $23 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization.

DESC is obligated with respect to an aggregate of $68 million of industrial revenue bonds which are secured by letters of credit. These letters of credit expire, subject to renewal, in the fourth quarter of 2024.

DESC, GENCO and Fuel Company each have intercompany credit facilities with Dominion Energy with a maximum capacity of $900 million, $200 million and $400 million, respectively. At March 31, 2024 and December 31, 2023, DESC, GENCO and Fuel Company

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collectively had borrowings outstanding under these agreements totaling $672 million and $442 million, respectively, which are recorded in affiliated and related party payables in DESC’s Consolidated Balance Sheets. Interest charges associated with these agreements were $10 million and $13 million for the three months ended March 31, 2024 and 2023, respectively.

6. INCOME TAXES

For continuing operations, including noncontrolling interests, the statutory U.S. federal income tax rate reconciles to DESC’s effective income tax rate as follows:

Three Months Ended March 31,	2024			2023
U.S. statutory rate		21.0	%		21.0	%
Increases (reductions) resulting from:
State taxes, net of federal benefit		3.9			4.1
Reversal of excess deferred income taxes		(5.3	)		(4.7	)
Allowance for equity funds used during construction		(0.7	)		—
Settlements of uncertain tax positions		—			(9.9	)
Other, net		—			(0.1	)
Effective tax rate		18.9	%		10.4	%

As of March 31, 2024, there have been no material changes in DESC’s unrecognized tax benefits or possible changes that could reasonably be expected to occur during the next twelve months. See Note 7 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023, for a discussion of these unrecognized tax benefits.

For the three months ended March 31, 2023, DESC’s effective tax rate reflects an income tax benefit of $11 million from the effective settlement of a position that management believed was reasonably possible to occur.

7. DERIVATIVE FINANCIAL INSTRUMENTS

DESC’s accounting policies, objectives, and strategies for using derivative instruments are discussed in Note 2 in the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023. See Note 8 for further information about fair value measurements and associated valuation methods for derivatives.

Cash collateral, as presented in the table below, is used to offset derivative assets and liabilities. Certain of DESC’s derivative instruments contain credit-related contingent provisions. These provisions require DESC to provide collateral upon the occurrence of specific events, primarily a credit rating downgrade. If the credit-related contingent features underlying the instruments that are in a liability position and not fully collateralized with cash were fully triggered as of March 31, 2024 and December 31, 2023, DESC would have been required to post $2 million and $4 million, respectively, of additional collateral to its counterparties. The collateral that would be required to be posted includes the impacts of any offsetting asset positions and any amounts already posted for derivatives and non-derivative contracts per contractual terms. DESC had not posted any collateral at March 31, 2024 and December 31, 2023 related to derivatives with credit-related contingent provisions that are in a liability position and not fully collateralized with cash. The aggregate fair value of all derivative instruments with credit-related contingent provisions that are in a liability position and not fully collateralized with cash as of March 31, 2024 and December 31, 2023 was $2 million and $4 million, respectively, which does not include the impact of any offsetting asset positions.

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The table below presents derivative balances by type of financial instrument, if the gross amounts recognized in the Consolidated Balance Sheets were netted with derivative instruments and cash collateral received or paid:

	March 31, 2024								December 31, 2023
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts		Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts
Interest rate contracts:
Over-the-counter	$	1	$	—	$	—	$	1	$	—	$	—	$	—	$	—
Commodity contracts:
Over-the-counter		9		—		—		9		—		—		—		—
Total derivatives	$	10	$	—	$	—	$	10	$	—	$	—	$	—	$	—

(1)Excludes derivative assets of $245 million and $176 million at March 31, 2024 and December 31, 2023, respectively, which are not subject to master netting or similar arrangements.

	March 31, 2024								December 31, 2023
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts		Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	4	$	—	$	—	$	4
Total derivatives	$	2	$	—	$	—	$	2	$	4	$	—	$	—	$	4

(1)DESC did not have any derivative liabilities at March 31, 2024 and December 31, 2023, respectively, which were not subject to master netting or similar arrangements.

Volumes

The following table presents the volume of derivative activity at March 31, 2024. These volumes are based on open derivative positions and represent the combined absolute value of their long and short positions.

	Current		Noncurrent
Natural Gas (bcf):
Basis(1)		24		—
Electricity (MWh in millions):
Fixed price		2		23
Interest rate(2) (in millions)	$	—	$	71

(1)Includes options.

(2)Maturity is determined based on final settlement period.

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Fair Value and Gains and Losses on Derivative Instruments

The following tables present the fair values of derivatives and where they are presented in the Consolidated Balance Sheets:

(millions)	Fair Value - Derivatives under Hedge Accounting		Fair Value - Derivatives not under Hedge Accounting		Total Fair Value
At March 31, 2024
ASSETS
Current Assets
Commodity	$	—	$	19	$	19
Total current derivative assets(1)		—		19		19
Noncurrent Assets
Commodity		—		235		235
Interest rate		—		1		1
Total noncurrent derivative assets(2)		—		236		236
Total derivative assets	$	—	$	255	$	255
LIABILITIES
Noncurrent Liabilities
Interest rate		—		2		2
Total noncurrent derivative liabilities(3)		—		2		2
Total derivative liabilities	$	—	$	2	$	2
At December 31, 2023
ASSETS
Current Assets
Commodity	$	—	$	9	$	9
Total current derivative assets(1)		—		9		9
Noncurrent Assets
Commodity		—		167		167
Interest rate		—		—		—
Total noncurrent derivative assets(2)		—		167		167
Total derivative assets	$	—	$	176	$	176
LIABILITIES
Noncurrent Liabilities
Interest rate		—		4		4
Total noncurrent derivative liabilities(3)		—		4		4
Total derivative liabilities	$	—	$	4	$	4

(1)Current derivative assets are presented in other current assets in DESC’s Consolidated Balance Sheets.

(2)Noncurrent derivative assets are presented in other deferred debits and other assets in DESC’s Consolidated Balance Sheets.

(3)Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in DESC’s Consolidated Balance Sheets.

The following tables present the gains and losses on derivatives, as well as where the associated activity is presented in the Consolidated Balance Sheets and Statements of Comprehensive Income:

Derivatives in Cash Flow Hedging Relationships

(millions)	Increase (Decrease) in Derivatives Subject to Regulatory Treatment(1)
Three Months Ended March 31,	2024		2023
Derivative type and location of gains (losses):
Interest rate	$	—	$	(1	)
Total	$	—	$	(1	)

(1)Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Derivatives Not Designated as Hedging Instruments

(millions)	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
Three Months Ended March 31,	2024			2023
Derivative type and location of gains (losses):
Commodity:
Purchased power	$	(2	)	$	1
Interest rate:
Interest charges		(1	)		—
Total	$	(3	)	$	1

(1)Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

8. FAIR VALUE MEASUREMENTS, INCLUDING DERIVATIVES

DESC’s fair value measurements are made in accordance with the policies discussed in Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023. See Note 7 in this report for further information about DESC’s derivatives and hedge accounting activities.

The following table presents DESC’s quantitative information about Level 3 fair value measurements at March 31, 2024. The range and weighted average are presented in dollars for market price inputs and percentages for price volatility.

	Fair Value (millions)		Valuation Techniques	Unobservable Input		Range	Weighted Average(1)
Assets
Physical forwards:
Electricity	$	246	Discounted cash flow	Market price (per MWh)	(3)	24-102	51
Physical options:
Natural gas(2)	$	7	Option model	Market price (per Dth)	(3)	1-3	2
				Price volatility	(4)	10%-51%	34%
Total assets	$	253

(1)Averages weighted by volume.

(2)Includes basis.

(3)Represents market prices beyond defined terms for Levels 1 and 2.

(4)Represents volatilities unrepresented in published markets.

Sensitivity of the fair value measurements to changes in the significant unobservable inputs is as follows:

Significant Unobservable Inputs	Position	Change to Input	Impact on Fair Value Measurement
Market price	Buy	Increase (decrease)	Gain (loss)
Market price	Sell	Increase (decrease)	Loss (gain)
Price volatility	Buy	Increase (decrease)	Gain (loss)
Price volatility	Sell	Increase (decrease)	Loss (gain)

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Recurring Fair Value Measurements

The following table presents DESC’s assets and liabilities that are measured at fair value on a recurring basis for each hierarchy level, including both current and noncurrent portions:

(millions)	Level 1		Level 2		Level 3		Total
At March 31, 2024
Assets
Commodity	$	—	$	1	$	253	$	254
Interest rate		—		1		—		1
Total assets	$	—	$	2	$	253	$	255
Liabilities
Interest rate	$	—	$	2	$	—	$	2
Total liabilities	$	—	$	2	$	—	$	2
At December 31, 2023
Assets
Commodity	$	—	$	—	$	176	$	176
Interest rate		—		—		—		—
Total assets	$	—	$	—	$	176	$	176
Liabilities
Interest rate	$	—	$	4	$	—	$	4
Total liabilities	$	—	$	4	$	—	$	4

The following table presents the net change in DESC’s assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

	Three Months Ended March 31,
	2024			2023
(millions)
Beginning balance	$	176		$	251
Total realized and unrealized gains (losses):
Included in earnings:
Purchased power		(2	)		1
Included in regulatory assets/liabilities		70			(63	)
Settlements		2			(1	)
Purchases		7			—
Ending balance	$	253		$	188

There are no unrealized gains and losses included in earnings in the Level 3 fair value category related to assets/liabilities still held at the reporting date for the three months ended March 31, 2024 and 2023.

Fair Value of Financial Instruments

Substantially all of DESC’s financial instruments are recorded at fair value, with the exception of the instruments described below, which are reported at historical cost. Estimated fair values have been determined using available market information and valuation methodologies considered appropriate by management. The carrying amount of financial instruments classified within current assets and current liabilities are representative of fair value because of the short-term nature of these instruments. For financial instruments that are not recorded at fair value, the carrying amounts and estimated fair values are as follows:

	March 31, 2024				December 31, 2023
(millions)	Carrying Amount		Estimated Fair Value(1)		Carrying Amount		Estimated Fair Value(1)
Long-term debt(2)	$	4,219	$	4,221	$	4,219	$	4,301
Affiliated long-term debt(3)		230		230		230		230

(1)Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

(2)Carrying amount includes current portions, if any, presented in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

(3)Carrying amount includes current portions presented in affiliated and related party payables.

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9. EMPLOYEE BENEFIT PLANS

In DESC’s Consolidated Statements of Comprehensive Income, the service cost component of net periodic benefit (credit) cost is reflected in other operations and maintenance expense with the non-service cost components reflected in other income. Components of net periodic benefit cost (credit) recorded by DESC were as follows:

(millions)	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2024			2023			2024			2023
Service cost	$	2		$	2		$	—		$	—
Interest cost		8			8			2			2
Expected return on assets		(9	)		(8	)		—			—
Amortization of actuarial losses		2			3			(1	)		(1	)
Net periodic benefit cost	$	3		$	5		$	1		$	1

During the three months ended March 31, 2024, DESC made no contributions to its pension trust. DESC expects to make $8 million of minimum required contributions to its qualified pension plan in 2024 and expects to receive reimbursement for such contributions from Santee Cooper. In April 2024, DESC made $1 million of contributions to its qualified pension plan. DESC recovers current pension costs through either a rate rider that may be adjusted annually for retail electric operations or through cost of service rates for gas operations.

10. COMMITMENTS AND CONTINGENCIES

As a result of issues generated in the ordinary course of business, DESC is involved in legal proceedings before various courts and is periodically subject to governmental examinations (including by regulatory authorities), inquiries and investigations. Certain legal proceedings and governmental examinations involve demands for unspecified amounts of damages, are in an initial procedural phase, involve uncertainty as to the outcome of pending appeals or motions, or involve significant factual issues that need to be resolved, such that it is not possible for DESC to estimate a range of possible loss. For such matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the litigation or investigative processes such that DESC is able to estimate a range of possible loss. For legal proceedings and governmental examinations that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. DESC maintains various insurance programs, including general liability insurance coverage which provides coverage for personal injury or wrongful death cases. Any accrued liability is recorded on a gross basis with a receivable also recorded for any probable insurance recoveries. Estimated ranges of loss are inclusive of legal fees and net of any anticipated insurance recoveries. Any estimated range is based on currently available information and involves elements of judgment and significant uncertainties. Any estimated range of possible loss may not represent DESC’s maximum possible loss exposure. The circumstances of such legal proceedings and governmental examinations will change from time to time and actual results may vary significantly from the current estimate. For current proceedings not specifically reported below, management does not anticipate that the liabilities, if any, arising from such proceedings would have a material effect on DESC’s financial position, liquidity or results of operations. During the three months ended March 31, 2024, DESC recorded $6 million of charges in aggregate for various personal injury or wrongful death cases.

Environmental Matters

DESC is subject to costs resulting from a number of federal, state and local laws and regulations designed to protect human health and the environment. These laws and regulations affect future planning and existing operations. They can result in increased capital, operating and other costs as a result of compliance, remediation, containment and monitoring obligations.

From a regulatory perspective, DESC continually monitors and evaluates its current and projected emission levels and strives to comply with all state and federal regulations regarding those emissions. DESC participates in the SO2 and NOx emission allowance programs with respect to coal plant emissions and also has constructed additional pollution control equipment at its coal-fired electric generating plants. These actions are expected to address many of the rules and regulations discussed herein.

Air

The CAA, as amended, is a comprehensive program utilizing a broad range of regulatory tools to protect and preserve the nation’s air quality. At a minimum, states are required to establish regulatory programs to meet applicable requirements of the CAA. However, states may choose to develop regulatory programs that are more restrictive. Many of DESC’s facilities are subject to the CAA’s permitting and other requirements.

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ACE Rule

In July 2019, the EPA published the final rule informally referred to as the ACE Rule, as a replacement for the Clean Power Plan. The ACE Rule regulated GHG emissions from existing coal-fired power plants pursuant to Section 111(d) of the CAA and required states to develop plans by July 2022 establishing unit-specific performance standards for existing coal-fired power plants. In January 2021, the U.S. Court of Appeals for the D.C. Circuit vacated the ACE Rule and remanded it to the EPA. This decision would take effect upon issuance of the court’s mandate. In March 2021, the court issued a partial mandate vacating and remanding all parts of the ACE Rule except for the portion of the ACE Rule that repealed the Clean Power Plan. In October 2021, the U.S. Supreme Court agreed to hear a challenge of the U.S. Court of Appeals for the D.C. Circuit’s decision on the ACE Rule. In June 2022, the U.S. Supreme Court reversed the D.C. Circuit’s decision on the ACE Rule and remanded the case back to the D.C. Circuit. In May 2023, the EPA proposed to repeal the ACE Rule as part of a package of proposed rules addressing CO2 emissions from new and existing fossil fuel-fired electric generating units. Until the EPA takes final action on this proposed rulemaking, DESC cannot predict an impact to its operations, financial condition and/or cash flows.

Carbon Regulations

In August 2016, the EPA issued a draft rule proposing to reaffirm that a source’s obligation to obtain a PSD or Title V permit for GHGs is triggered only if such permitting requirements are first triggered by non-GHG, or conventional, pollutants that are regulated by the New Source Review program, and exceed a significant emissions rate of 75,000 tons per year of CO2 equivalent emissions. Until the EPA ultimately takes final action on this rulemaking, DESC cannot predict the impact to its results of operations, financial condition and/or cash flows.

In December 2018, the EPA proposed revised Standards of Performance for Greenhouse Gas Emissions from New, Modified, and Reconstructed Stationary Sources. The proposed rule would amend the previous determination that the best system of emission reduction for newly constructed coal-fired steam generating units is no longer partial carbon capture and storage. Instead, the proposed revised best system of emission reduction for this source category is the most efficient demonstrated steam cycle (e.g., supercritical steam conditions for large units and subcritical steam conditions for small units) in combination with best operating practices. The proposed revision to the performance standards for coal-fired steam generating units remains pending. Until the EPA ultimately takes final action on this rulemaking, DESC cannot predict the impact to its results of operations, financial condition and/or cash flows.

Water

The CWA, as amended, is a comprehensive program requiring a broad range of regulatory tools including a permit program to authorize and regulate discharges to surface waters with strong enforcement mechanisms. DESC must comply with applicable aspects of the CWA programs at its operating facilities.

Regulation 316(b)

In October 2014, the final regulations under Section 316(b) of the CWA that govern existing facilities and new units at existing facilities that employ a cooling water intake structure and that have flow levels exceeding a minimum threshold became effective. The rule establishes a national standard for impingement based on seven compliance options, but forgoes the creation of a single technology standard for entrainment. Instead, the EPA has delegated entrainment technology decisions to state regulators. State regulators are to make case-by-case entrainment technology determinations after an examination of five mandatory facility-specific factors, including a social cost-benefit test, and six optional facility-specific factors. The rule governs all electric generating stations with water withdrawals above two MGD, with a heightened entrainment analysis for those facilities over 125 MGD. DESC has five facilities that are subject to the final regulations. DESC is also working with the EPA and state regulatory agencies to assess the applicability of Section 316(b) to five hydroelectric facilities. DESC anticipates that it may have to install impingement control technologies at certain of these stations that have once-through cooling systems. DESC is currently evaluating the need or potential for entrainment controls under the final rule as these decisions will be made on a case-by-case basis after a thorough review of detailed biological, technological, and cost benefit studies. DESC is conducting studies and implementing plans as required by the rule to determine appropriate intake structure modifications at certain facilities to ensure compliance with this rule. While the impacts of this rule could be material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Effluent Limitations Guidelines

In September 2015, the EPA released a final rule to revise the ELG Rule. The final rule established updated standards for wastewater discharges that apply primarily at coal and oil steam generating stations. Affected facilities are required to convert from wet to dry or closed cycle coal ash management, improve existing wastewater treatment systems and/or install new wastewater treatment technologies in order to meet the new discharge limits. In April 2017, the EPA granted two separate petitions for reconsideration of the final ELG Rule and stayed future compliance dates in the rule. Also in April 2017, the U.S. Court of Appeals for the Fifth Circuit granted the EPA’s request for a stay of the pending consolidated litigation challenging the rule while the EPA addresses the petitions

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for reconsideration. In September 2017, the EPA signed a rule to postpone the earliest compliance dates for certain waste streams regulations in the final ELG Rule from November 2018 to November 2020; however, the latest date for compliance for these regulations was December 2023. In October 2020, the EPA released the final rule that extends the latest dates for compliance. Individual facilities’ compliance dates will vary based on circumstances and the determination by state regulators and may range from 2021 to 2028. While the impacts of this rule could be material to DESC’s results of operations, financial condition and/or cash flows, as DESC expects that wastewater treatment technology retrofits and modifications at the Williams and Wateree generating stations will be required, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Capacity Use Area

In November 2019, a new CUA was established in the counties surrounding the Cope Generating Station (Western Capacity Use Area) under the South Carolina Groundwater Use and Reporting Regulation. Under the regulation any groundwater well in a CUA that withdraws above three million gallons per month must be permitted. The Cope Generating Station is located within this new Western Capacity Use Area. Cope has been using four deep groundwater wells for cooling water and other house loads since 1996. Prior to designation of the new Western Capacity Use Area, the wells at Cope Station were only required to be registered not permitted. As a result of this designation, Cope will need to restore the surface water equipment to operable status to reduce reliance on groundwater wells. This includes completion of 316(b) requirements, (including SCDHEC BACT determination and modification of the station national pollutant discharge elimination system permit) and extensive inspection, repair and/or replacement of the associated surface water withdrawal equipment which has been idle since 1996. While the impacts of this rule change are potentially material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Waste Management and Remediation

The operations of DESC are subject to a variety of state and federal laws and regulations governing the management and disposal of solid and hazardous waste, and release of hazardous substances associated with current and/or historical operations. The CERCLA, as amended, and similar state laws, may impose joint, several and strict liability for cleanup on potentially responsible parties who owned, operated or arranged for disposal at facilities affected by a release of hazardous substances. In addition, many states have created programs to incentivize voluntary remediation of sites where historical releases of hazardous substances are identified and property owners or responsible parties decide to initiate cleanups.

From time to time, DESC may be identified as a potentially responsible party in connection with the alleged release of hazardous substances or wastes at a site. Under applicable federal and state laws, DESC could be responsible for costs associated with the investigation or remediation of impacted sites, or subject to contribution claims by other responsible parties for their costs incurred at such sites. DESC also may identify, evaluate and remediate other potentially impacted sites under voluntary state programs. Remediation costs may be subject to reimbursement under DESC’s insurance policies, rate recovery mechanisms, or both. Except as described below, DESC does not believe these matters will have a material effect on results of operations, financial condition and/or cash flows.

DESC has four decommissioned manufactured gas plant sites in South Carolina that are in various states of investigation, remediation and monitoring under work plans approved by, or under review by, the SCDHEC or the EPA. In the fourth quarter of 2023, DESC completed the majority of remediation activities at one site. DESC anticipates the remaining activities at that site will be completed by 2025 at an estimated cost of $5 million, after which the site will continue to incur ongoing maintenance and monitoring obligations. DESC expects to recover costs arising from the remediation work at all four sites through rate recovery mechanisms and as of March 31, 2024, deferred amounts, net of amounts previously recovered through rates and insurance settlements, totaled $34 million and are included in regulatory assets.

Ash Pond and Landfill Closure Costs

In April 2015, the EPA enacted a final rule regulating CCR landfills, existing ash ponds that still receive and manage CCRs, and inactive ash ponds that do not receive, but still store, CCRs. DESC currently has inactive and existing CCR ponds and CCR landfills subject to the final rule at three different facilities. This rule created a legal obligation for DESC to retrofit or close all of its inactive and existing ash ponds over a certain period of time, as well as perform required monitoring, corrective action, and post-closure care activities as necessary.

In December 2016, legislation was enacted that creates a framework for EPA-approved state CCR permit programs. In August 2017, the EPA issued interim guidance outlining the framework for state CCR program approval. The EPA has enforcement authority until state programs are approved. The EPA and states with approved programs both will have authority to enforce CCR requirements under their respective rules and programs. In September 2017, the EPA agreed to reconsider portions of the CCR rule in response to two petitions for reconsideration. In March 2018, the EPA proposed certain changes to the CCR rule related to issues remanded as part of the pending litigation and other issues the EPA is reconsidering. Several of the proposed changes would allow states with approved CCR permit programs additional flexibility in implementing their programs. In July 2018, the EPA promulgated the first phase of changes to the CCR rule. In August 2018, the U.S. Court of Appeals for the D.C. Circuit issued its decision in the pending challenges

22

of the CCR rule, vacating and remanding to the EPA three provisions of the rule. Until this matter is resolved and all phases of the CCR rule are promulgated, DESC is unable to precisely estimate potential incremental impacts or costs related to existing coal ash sites in connection with future implementation of the final CCR rule. In May 2023, the EPA released a proposed rule addressing one of the previously remanded provisions of the CCR rule to regulate inactive surface impoundments located at retired generating stations that contained CCR and liquids after October 2015, and certain other inactive or previously closed surface impoundments, landfills or other areas that contain accumulations of CCR. Until the EPA ultimately takes final action on this rulemaking, DESC is unable to predict whether or to what extent the new rules will ultimately require additional controls. While such amounts may be material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts.

Claims and Litigation

The following describes certain legal proceedings involving DESC relating primarily to events occurring before closing of the SCANA Combination.

Matters Fully Resolved Prior to 2024 Impacting the Consolidated Financial Statements

Governmental Proceedings and Investigations

In June 2018, DESC received a notice of proposed assessment of approximately $410 million, excluding interest, from the SCDOR following its audit of DESC’s sales and use tax returns for the periods September 1, 2008 through December 31, 2017. The proposed assessment, which includes 100% of the NND Project, is based on the SCDOR’s position that DESC’s sales and use tax exemption for the NND Project does not apply because the facility will not become operational. In December 2020, the parties reached an agreement in principle in the amount of $165 million to resolve this matter. In June 2021, the parties executed a settlement agreement which allows DESC to fund the settlement amount through a combination of cash, shares of Dominion Energy common stock or real estate with an initial payment of at least $43 million in shares of Dominion Energy common stock. In August 2021, Dominion Energy issued 0.6 million shares of its common stock to satisfy DESC’s obligation for the initial payment under the settlement agreement. In May 2022, Dominion Energy issued an additional 0.9 million shares of its common stock to partially satisfy DESC’s remaining obligation under the settlement agreement. In June 2022, DESC requested approval from the South Carolina Commission to transfer certain real estate with a total settlement value of $51 million to satisfy its remaining obligation under the settlement agreement. In July 2022, the South Carolina Commission voted to approve the request and issued its final order in August 2022. In September 2022, DESC transferred certain non-utility property with a fair value of $28 million to the SCDOR under the settlement agreement. In December 2022, DESC transferred additional utility property with a fair value of $3 million to the SCDOR. In October 2022, DESC filed for approval to transfer the remaining real estate with FERC which was received in November 2022. In March 2023, DESC transferred utility property with a fair value of $10 million to the SCDOR resulting in a gain of $9 million ($7 million after-tax), recorded in other income, net in DESC’s Consolidated Statements of Comprehensive Income for the three months ended March 31, 2023. In June 2023, DESC transferred the remaining utility property with a fair value of $11 million to the SCDOR. In July 2023, DESC made a less than $1 million cash payment to the SCDOR to fully satisfy its remaining obligation, including applicable interest, under the settlement agreement.

Nuclear Operations

Other than the items discussed below, there have been no significant changes regarding DESC’s nuclear insurance and spent nuclear fuel as described in Note 12 to the Consolidated Financial Statements in the DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

During the first quarter of 2024, the total liability protection per nuclear incident available to all participants in the Secondary Financial Protection Program increased from $16.2 billion to $16.3 billion. This increase does not impact DESC’s responsibility per active unit under the Price-Anderson Amendments Act of 1988. Additionally, Dominion Energy increased the amount of coverage purchased from commercial insurance pools for Summer from $450 million to $500 million with the remainder provided through the mandatory industry retrospective rating plan.

Surety Bonds

At March 31, 2024, DESC had purchased $24 million of surety bonds. Under the terms of surety bonds, DESC is obligated to indemnify the respective surety bond company for any amounts paid.

23

11. OPERATING SEGMENTS

The Corporate and Other segment primarily includes specific items attributable to DESC’s operating segment that are not included in profit measures evaluated by executive management in assessing the segment’s performance or in allocating resources.

In the three months ended March 31, 2024 and 2023, DESC reported an insignificant amount of specific items in the Corporate and Other segment.

(millions)	External Revenue		Comprehensive Income (Loss) Available (Attributable) to Common Shareholder
Three Months Ended March 31, 2024
Dominion Energy South Carolina	$	775	$	75
Corporate and Other		—		(1	)
Consolidated total	$	775	$	74
Three Months Ended March 31, 2023
Dominion Energy South Carolina	$	759	$	86
Corporate and Other		—		6
Consolidated total	$	759	$	92

12. AFFILIATED AND RELATED PARTY TRANSACTIONS

DES, on behalf of itself and its parent company, provides the following services to DESC, which are rendered at direct or allocated cost: information systems, telecommunications, customer support, marketing and sales, human resources, corporate compliance, purchasing, financial, risk management, public affairs, legal, investor relations, gas supply and capacity management, strategic planning, general administrative and retirement benefits. Costs for these services include amounts capitalized. Amounts expensed are primarily recorded in other operations and maintenance - affiliated suppliers and other income, net in the Consolidated Statements of Comprehensive Income.

DESC transacts with affiliates for certain quantities of electricity in the ordinary course of business. DESC also enters into certain commodity derivative contracts with affiliates. DESC uses these contracts, which are principally comprised of forward commodity purchases, to manage commodity price risks associated with purchases of electricity. See Note 7 for additional information.

	Three Months Ended March 31,
(millions)	2024		2023
Direct and allocated costs from DES(1)	$	53	$	57
Operating Revenues - Electric from sales to affiliate		1		1
Operating Expenses - Other taxes from affiliate		3		3
Purchases of electricity from solar affiliates		1		2

(1)Includes capitalized expenditures of $12 million and $16 million for the three months ended March 31, 2024 and 2023, respectively.

(millions)	March 31, 2024		December 31, 2023
Payable to DES		41		18
Payable to SCANA Corporation		7		7
Payable to Public Service Company of North Carolina, Incorporated		12		13
Derivative assets with affiliates(1)		42		33

(1)Includes amounts recorded in other current assets of $2 million as of both March 31, 2024 and December 31, 2023 and amounts recorded in other deferred debits and other assets of $40 million and $31 million as of March 31, 2024 and December 31, 2023, respectively.

Borrowings from an affiliate are described in Note 5.

24

13. OTHER INCOME, NET

Components of other income, net are as follows:

	Three Months Ended March 31,
(millions)	2024			2023
Other income	$	2		$	2
Gains on sales of assets(1)		1			10
Other expense		(5	)		(2	)
Allowance for equity funds used during construction		3			—
Other income, net	$	1		$	10

(1) Includes amounts recognized in 2023 in connection with the transfer of property to satisfy litigation. See Note 10 for additional information.

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ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

MD&A discusses DESC’s results of operations. MD&A should be read in conjunction with DESC’s Consolidated Financial Statements. DESC meets the conditions to file under the reduced disclosure format, and therefore has omitted certain sections of MD&A.

Contents of MD&A

MD&A consists of the following information:

•Forward-Looking Statements

•Results of Operations

Forward-Looking Statements

This report contains statements concerning DESC’s expectations, plans, objectives, future financial performance and other statements that are not historical facts. These statements are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. In most cases, the reader can identify these forward-looking statements by such words as “path,” “anticipate,” “estimate,” “forecast,” “expect,” “believe,” “should,” “could,” “plan,” “may,” “continue,” “target” or other similar words.

DESC makes forward-looking statements with full knowledge that risks and uncertainties exist that may cause actual results to differ materially from predicted results. Factors that may cause actual results to differ are often presented with the forward-looking statements themselves. Additionally, other factors may cause actual results to differ materially from those indicated in any forward-looking statement. These factors include but are not limited to:

•Unusual weather conditions and their effect on energy sales to customers and energy commodity prices;

•Extreme weather events and other natural disasters, including, but not limited to, hurricanes, high winds, severe storms, earthquakes, flooding, wildfires, climate changes and changes in water temperatures and availability that can cause outages and property damage to facilities;

•The impact of extraordinary external events, such as the pandemic health event resulting from COVID-19, and their collateral consequences, including extended disruption of economic activity in DESC’s markets and global supply chains;

•Federal, state and local legislative and regulatory developments, including changes in or interpretations of federal and state tax laws and regulations;

•The indirect impacts of Dominion Energy implementing recommendations resulting from its business review concluded in March 2024;

•Risks of operating businesses in regulated industries that are subject to changing regulatory structures;

•Changes to regulated rates collected;

•Changes in future levels of domestic and international natural gas production, supply or consumption;

•Timing and receipt of regulatory approvals necessary for planned construction or growth projects and compliance with conditions associated with such regulatory approvals;

•The inability to complete planned construction, conversion or growth projects at all, or with the outcomes or within the terms and time frames initially anticipated, including as a result of increased public involvement, intervention or litigation in such projects;

•Changes to federal, state and local environmental laws and regulations, including those related to climate change, the tightening of emission or discharge limits for GHGs and other substances, more extensive permitting requirements and the regulation of additional substances;

•Cost of environmental strategy and compliance, including those costs related to climate change;

•Changes in implementation and enforcement practices of regulators relating to environmental standards and litigation exposure for remedial activities;

•Difficulty in anticipating mitigation requirements associated with environmental and other regulatory approvals or related appeals;

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•The impact of operational hazards, including adverse developments with respect to pipeline and plant safety or integrity, equipment loss, malfunction or failure, operator error, and other catastrophic events;

•Risks associated with the operation of nuclear facilities, including costs associated with the disposal of spent nuclear fuel, decommissioning, plant maintenance and changes in existing regulations governing such facilities;

•Changes in operating, maintenance and construction costs;

•Domestic terrorism and other threats to DESC’s physical and intangible assets, as well as threats to cybersecurity;

•Additional competition from the development and deployment of alternative energy sources, such as self-generation and distributed generation technologies;

•Competition in the development, construction and ownership of certain electric transmission facilities in connection with Order 1000;

•Changes in technology, particularly with respect to new, developing or alternative sources of generation and smart grid technologies;

•Changes in demand for services, including industrial, commercial and residential growth or decline in service areas, changes in supplies of natural gas delivered, changes in customer growth or usage patterns, including as a result of energy conservation programs, the availability of energy efficient devices and the use of distributed generation methods;

•Adverse outcomes in litigation matters or regulatory proceedings;

•Counterparty credit and performance risk;

•Fluctuations in the value of investments held in nuclear decommissioning and benefit plan trusts;

•Fluctuations in energy-related commodity prices and the effect these could have on DESC’s liquidity position and the underlying value of its assets;

•Fluctuations in interest rates;

•Changes in rating agency requirements or credit ratings and their effect on availability and cost of capital;

•Global capital market conditions, including the availability of credit and the ability to obtain financing on reasonable terms;

•Political and economic conditions, including inflation and deflation;

•Employee workforce factors including collective bargaining agreements and labor negotiations with union employees; and

•Changes in financial or regulatory accounting principles or policies imposed by governing bodies.

Additionally, other risks that could cause actual results to differ from predicted results are set forth in Part I. Item 1A. Risk Factors in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

DESC’s forward-looking statements are based on beliefs and assumptions using information available at the time the statements are made. DESC cautions the reader not to place undue reliance on its forward-looking statements because the assumptions, beliefs, expectations and projections about future events may, and often do, differ materially from actual results. DESC undertakes no obligation to update any forward-looking statement to reflect developments occurring after the statement is made.

Results of Operations

Presented below is a summary of DESC’s results:

	First Quarter
(millions)	2024		2023		$ Change
Net income	$	80	$	97	$	(17	)

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Overview

First Quarter 2024 vs. 2023

Net income decreased 18%, primarily due to various factors, including the absence of a benefit associated with the effective settlement of an uncertain tax position, increased interest rates on bonds and a decrease in gains from the sale of certain utility property, partially offset by an increase in sales to utility customers from weather and other customer-related factors.

Analysis of Consolidated Operations

Presented below are selected amounts related to DESC’s results of operations:

	First Quarter
(millions)	2024		2023		$ Change
Operating revenues	$	775	$	759	$	16
Fuel used in electric generation		145		150		(5	)
Purchased power		10		7		3
Gas purchased for resale		79		82		(3	)
Other operations and maintenance		163		156		7
Depreciation and amortization		136		129		7
Other taxes		78		78		—
Other income, net		1		10		(9	)
Interest charges		67		59		8
Income tax expense		18		11		7

An analysis of DESC’s results of operations follows:

First Quarter 2024 vs. 2023

Operating revenues increased 2%, primarily reflecting:

•A $13 million increase in sales to electric utility retail customers from an increase in heating degree days during the heating season;

•An $11 million increase in sales to gas utility customers associated with economic and other usage factors; and

•A $6 million increase in sales to electric utility retail customers associated with growth; partially offset by

•A $10 million decrease in fuel-related revenue as a result of a decrease in commodity costs and purchased power costs associated with sales to electric utility retail customers ($7 million) and gas utility customers ($3 million).

Other operations and maintenance increased 4%, primarily due to charges associated with various personal injury or wrongful death litigation cases ($6 million) and an increase in salaries, wages and benefits and administrative expenses ($5 million).

Other income, net decreased 90%, primarily due to a decrease in gains from the sale of certain utility property.

Interest charges increased 14%, primarily due to an increase in principal and interest rates on bonds.

Income tax expense increased 64%, primarily due to the absence of a benefit associated with the effective settlement in 2023 of an uncertain tax position.

ITEM 4. CONTROLS AND PROCEDURES

Senior management of DESC, including DESC’s CEO and CFO, evaluated the effectiveness of DESC’s disclosure controls and procedures as of the end of the period covered by this report. Based on this evaluation process, DESC’s CEO and CFO have concluded that DESC’s disclosure controls and procedures are effective.

There were no changes that occurred during the last fiscal quarter that materially affected, or are reasonably likely to materially affect, DESC’s internal control over financial reporting.

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PART II. OTHER INFORMATION

ITEM 1. LEGAL PROCEEDINGS

From time to time, DESC is party to various legal, environmental or other regulatory proceedings, including in the ordinary course of business. SEC regulations require disclosure of certain environmental matters when a governmental authority is a party to the proceedings and such proceedings involve potential monetary sanctions that DESC reasonably believes will exceed a specified threshold. Pursuant to the SEC regulations, DESC uses a threshold of $1 million for such proceedings.

See the following for discussions on various legal, environmental and other regulatory proceedings to which DESC is a party, which information is incorporated herein by reference:

•Notes 3 and 12 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

•Notes 2 and 10 to the Consolidated Financial Statements in this report.

ITEM 1A. RISK FACTORS

DESC’s business is influenced by many factors that are difficult to predict, involve uncertainties that may materially affect actual results and are often beyond its control. A number of these risk factors have been identified in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023, which should be taken into consideration when reviewing the information contained in this report. There have been no material changes with regard to the risk factors previously disclosed in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023. For other factors that may cause actual results to differ materially from those indicated in any forward-looking statement or projection contained in this report, see Forward-Looking Statements in MD&A in this report.

ITEM 5. OTHER INFORMATION

During the last fiscal quarter, none of DESC’s directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408(a) of Regulation S-K.

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ITEM 6. EXHIBITS

Exhibit No.	Description
3.1	Amended and Restated Articles of Incorporation, effective April 29, 2019 (Exhibit 3.1, Form 8-K filed April 29, 2019, File No. 1-3375).
3.2	Amended and Restated Bylaws, effective April 29, 2019 (Exhibit 3.2, Form 8-K filed April 29, 2019, File No. 1-3375).
4.1	Dominion Energy South Carolina, Inc. agrees to furnish to the U.S. Securities and Exchange Commission upon request any instrument with respect to long-term debt as to which the total amount of securities authorized does not exceed 10% of its total consolidated assets.
31.a	Certification by Chief Executive Officer of Dominion Energy South Carolina, Inc. pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (filed herewith).
31.b	Certification by Chief Financial Officer of Dominion Energy South Carolina, Inc. pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (filed herewith).
32.a	Certification to the Securities and Exchange Commission by Chief Executive Officer and Chief Financial Officer of Dominion Energy South Carolina, Inc. as required by Section 906 of the Sarbanes-Oxley Act of 2002 (furnished herewith).
101	The following financial statements from Dominion Energy South Carolina, Inc.’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2024, filed on May 2, 2024, formatted in iXBRL (Inline eXtensible Reporting Language): (i) Consolidated Balance Sheets, (ii) Consolidated Statements of Comprehensive Income, (iii) Consolidated Statements of Cash Flows, (iv) Consolidated Statements of Changes in Common Equity, and (v) the Notes to Consolidated Financial Statements.
104	Cover Page Interactive Data File (formatted in iXBRL (Inline eXtensible Reporting Language) and contained in Exhibit 101).

30

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

	DOMINION ENERGY SOUTH CAROLINA, INC.
		(Registrant)
	By:	/s/ Michele L. Cardiff
Date: May 2, 2024		Michele L. Cardiff
		Senior Vice President, Controller and Chief Accounting Officer

31

EX-31.A

Exhibit 31.a

I, Diane Leopold, certify that:

1. I have reviewed this report on Form 10-Q of Dominion Energy South Carolina, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: May 2, 2024	/s/ Diane Leopold
	Diane Leopold Chief Executive Officer

EX-31.B

Exhibit 31.b

I, Steven D. Ridge, certify that:

1. I have reviewed this report on Form 10-Q of Dominion Energy South Carolina, Inc.;

2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4. The registrant's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

5. The registrant's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

Date: May 2, 2024	/s/ Steven D. Ridge
	Steven D. Ridge Executive Vice President and Chief Financial Officer

EX-32.A

Exhibit 32.a

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350,
AS ADOPTED PURSUANT TO
SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

Pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, each of the undersigned officers of Dominion Energy South Carolina, Inc. (the “Company”), certify that:

1.the Quarterly Report on Form 10-Q for the quarter ended March 31, 2024 (the “Report”), of the Company to which this certification is an exhibit fully complies with the requirements of section 13(a) or 15(d) of the Securities Exchange Act of 1934 (15 U.S.C. 78m(a) or 78o(d)).

2.the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of March 31, 2024, and for the period then ended.

/s/ Diane Leopold

Diane Leopold
Chief Executive Officer
May 2, 2024

/s/ Steven D. Ridge

Steven D. Ridge
Executive Vice President and
Chief Financial Officer
May 2, 2024

XML

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	Apr. 26, 2024
Cover [Abstract]
Entity Registrant Name	DOMINION ENERGY SOUTH CAROLINA, INC.
Entity Central Index Key	0000091882
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		40,296,147
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-3375
Entity Tax Identification Number	57-0248695
Entity Address, Address Line One	220 OPERATION WAY
Entity Address, City or Town	CAYCE
Entity Address, State or Province	SC
Entity Address, Postal Zip Code	29033
City Area Code	804
Local Phone Number	819-2284
Entity Incorporation, State or Country Code	SC
Document Quarterly Report	true
Document Transition Report	false
Entity Interactive Data Current	Yes
Document Period End Date	Mar. 31, 2024

XML

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
ASSETS
Utility plant in service		$ 15,570	$ 15,500
Accumulated depreciation and amortization		(5,591)	(5,557)
Construction work in progress		702	606
Nuclear fuel, net of accumulated amortization		226	229
Utility plant, net		10,907	10,778
Nonutility Property and Investments:
Nonutility property, net of accumulated depreciation		24	24
Assets held in trust, nuclear decommissioning		254	247
Nonutility property and investments, net		278	271
Current Assets:
Cash and cash equivalents		4	1
Customer, net of allowance for uncollectible accounts of $8 and $6		399	420
Receivables, other		63	97
Inventories (at average cost):
Fuel		92	94
Gas stored		22	30
Materials and supplies		243	232
Prepayments		78	84
Regulatory assets		351	444
Other current assets	[1]	30	23
Total current assets		1,285	1,429
Deferred Debits and Other Assets:
Regulatory assets		3,094	3,107
Affiliated receivables		4	4
Other	[1]	339	268
Total deferred debits and other assets		3,437	3,379
Total assets		15,907	15,857
CAPITALIZATION AND LIABILITIES
Common Stock - no par value		4,088	4,088
Retained earnings		604	592
Accumulated other comprehensive loss		(1)	(1)
Total common equity		4,691	4,679
Noncontrolling interest		189	183
Total equity		4,880	4,862
Long-term debt, net		4,219	4,219
Finance leases		3	4
Total long-term debt		4,222	4,223
Total capitalization		9,102	9,085
Current Liabilities:
Short-term borrowings		210	254
Securities due within one year		3	3
Accounts payable		135	180
Affiliated and related party payables		1,013	740
Customer deposits and customer prepayments		71	75
Taxes accrued		71	248
Interest accrued		81	79
Regulatory liabilities		233	205
Other		133	166
Total current liabilities		1,950	1,950
Deferred Credits and Other Liabilities:
Deferred income taxes and investment tax credits		1,323	1,318
Asset retirement obligations		734	731
Pension and other postretirement benefits		114	115
Regulatory liabilities		2,598	2,579
Other		86	79
Total deferred credits and other liabilities		4,855	4,822
Commitments and Contingencies
Total capitalization and liabilities		15,907	15,857
Related Party
Current Assets:
Affiliated and related party		$ 3	$ 4

[1] See Note 12 for amounts attributable to affiliates.

XML

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Utility plant, net	$ 10,907	$ 10,778
Receivables, customer, allowance for uncollectible accounts	8	6
Total current assets	1,285	1,429
Total deferred debits and other assets	$ 3,437	$ 3,379
Common stock, par value	$ 0	$ 0
Common stock, shares outstanding	40.3	40.3
Variable Interest Entity, Primary Beneficiary [Member]
Utility plant, net	$ 788	$ 773
Total current assets	87	89
Total deferred debits and other assets	$ 26	$ 26

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Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Operating Revenue	[1]	$ 775	$ 759
Operating Expenses:
Fuel used in electric generation		145	150
Purchased power	[1]	10	7
Gas purchased for resale		79	82
Other operations and maintenance		122	115
Other operations and maintenance - affiliated suppliers		41	41
Depreciation and amortization		136	129
Other taxes	[1]	78	78
Total operating expenses		611	602
Operating income		164	157
Other income (expense), net		1	10
Interest charges, net of AFUDC	[1]	67	59
Income before income tax expense		98	108
Income tax expense		18	11
Net Income and Other Comprehensive Income		80	97
Comprehensive Income Attributable to Noncontrolling Interest		6	5
Comprehensive Income Available to Common Shareholder		$ 74	$ 92

[1] See Note 12 for amounts attributable to affiliates.

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Consolidated Statements of Comprehensive Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Allowance for funds used during construction	$ 4	$ 4

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Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Operating Activities
Net income		$ 80	$ 97
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes, net		5	5
Depreciation and amortization		136	129
Amortization of nuclear fuel		9	9
Other adjustments		0	(7)
Changes in certain assets and liabilities:
Receivables		45	91
Receivables - affiliated and related party		1	1
Inventories		(1)	0
Prepayments		2	5
Regulatory assets		79	56
Regulatory liabilities		41	(122)
Accounts payable		(18)	(87)
Accounts payable - affiliated and related party		43	11
Taxes accrued		(177)	(165)
Interest accrued		2	(7)
Pension and other postretirement benefits		(1)	0
Other assets and liabilities		(80)	56
Net cash provided by operating activities		166	72
Investing Activities
Property additions and construction expenditures		(268)	(283)
Proceeds from investments and sales of assets		(13)	(8)
Purchase of investments		(5)	(4)
Other		0	1
Net cash used in investing activities		(286)	(294)
Financing Activities
Dividend to parent		(62)	(50)
Short-term borrowings, net		(44)	28
Short-term borrowings - affiliated, net		230	235
Other		(1)	1
Net cash provided by financing activities		123	214
Net increase (decrease) in cash, restricted cash and equivalents		3	(8)
Cash, restricted cash and equivalents at beginning of period	[1]	1	11
Cash, restricted cash and equivalents at end of period	[1]	4	3
Significant noncash investing and financing activities:
Accrued construction expenditures	[2]	$ 56	$ 54

[1] At March 31, 2024, December 31, 2023, March 31, 2023 and December 31, 2022 there were no restricted cash and equivalent balances.

[2] See Note 10 for noncash investing activities related to the transfer of property associated with the settlement of litigation.

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Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Statement of Cash Flows [Abstract]
Restricted cash and equivalents	$ 0	$ 0	$ 0	$ 0

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Consolidated Statements of Changes in Common Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Retained Earnings	AOCI	Noncontrolling Interest
Beginning balance at Dec. 31, 2022	$ 4,666	$ 4,088	$ 418	$ (2)	$ 162
Beginning balance (in shares) at Dec. 31, 2022		40
Total comprehensive income available to common shareholder	97		92		5
Dividend to parent	(50)		(50)
Ending balance at Mar. 31, 2023	4,713	$ 4,088	460	(2)	167
Ending balance (in shares) at Mar. 31, 2023		40
Beginning balance at Dec. 31, 2023	4,862	$ 4,088	592	(1)	183
Beginning balance (in shares) at Dec. 31, 2023		40
Total comprehensive income available to common shareholder	80		74		6
Dividend to parent	(62)		(62)
Ending balance at Mar. 31, 2024	$ 4,880	$ 4,088	$ 604	$ (1)	$ 189
Ending balance (in shares) at Mar. 31, 2024		40

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Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ 74	$ 92

XML

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

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Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Basis of Consolidation and Variable Interest Entities

DESC has determined that it has a controlling financial interest in each of GENCO and Fuel Company (which are considered to be VIEs) and, accordingly, DESC’s Consolidated Financial Statements include, after eliminating intercompany balances and transactions, the accounts of DESC, GENCO and Fuel Company. See Note 2 to the Consolidated Financial Statements included in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for a description of GENCO and Fuel Company.

DESC purchases shared services from DES, an affiliated VIE that provides accounting, legal, finance and certain administrative and technical services to all Dominion Energy subsidiaries, including DESC. DESC has determined that it is not the primary beneficiary of DES as it does not have either the power to direct the activities that most significantly impact its economic performance or an obligation to absorb losses and benefits which could be significant to it. See Note 12 for amounts attributable to affiliates.

Significant Accounting Policies

There have been no significant changes from Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023, except as follows.

New Accounting Standards

Climate-Related Disclosures

In March 2024, the SEC issued guidance for climate-related disclosures. The guidance requires disclosure of the financial statement impacts of severe weather events and other natural conditions, including amounts capitalized or expensed as well as any associated recoveries. In addition, the guidance requires disclosure of amounts related to renewable energy credits or carbon offsets if utilized as a material component of plans to achieve climate-related targets or goals. This guidance, which is currently subject to a stay issued by the SEC, would be effective for the fiscal year beginning January 1, 2025. DESC expects this guidance to only impact its disclosures with no impacts to its results of operations, cash flows or financial condition.

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Rate and Other Regulatory Matters

3 Months Ended

Mar. 31, 2024

Regulated Operations [Abstract]

Rate and Other Regulatory Matters

2. RATE AND OTHER REGULATORY MATTERS

Regulatory Matters Involving Potential Loss Contingencies

As a result of issues generated in the ordinary course of business, DESC is involved in various regulatory matters. Certain regulatory matters may ultimately result in a loss; however, as such matters are in an initial procedural phase, involve uncertainty as to the outcome of pending reviews or orders, and/or involve significant factual issues that need to be resolved, it is not possible for DESC to estimate a range of possible loss. For regulatory matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the regulatory process such that DESC is able to estimate a range of possible loss. For regulatory matters that DESC is able to reasonably estimate a range of possible losses, an

estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. Any estimated range is based on currently available information, involves elements of judgment and significant uncertainties and may not represent DESC’s maximum possible loss exposure. The circumstances of such regulatory matters will change from time to time and actual results may vary significantly from the current estimate. For current matters not specifically reported below, management does not anticipate that the outcome from such matters would have a material effect on DESC’s financial position, liquidity or results of operations.

Other Regulatory Matters

Other than the following matters, there have been no significant developments regarding the pending regulatory matters disclosed in Note 3 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

Electric Base Rate Case

In March 2024, DESC filed its retail electric base rate case and schedules with the South Carolina Commission. DESC proposed a non-fuel, base rate increase of $295 million, partially offset by a net decrease in storm damage and DSM components of $4 million. If approved, the overall proposed rate increase of $291 million, or 12.59%, would be effective on and after the first billing cycle of September 2024. The base rate increase was proposed to recover the significant investment in assets and operating resources required to serve an expanding customer base, maintain the safety, reliability and efficiency of DESC’s system and meet increasingly stringent reliability, security and environmental requirements for the benefit of South Carolina customers. DESC presented an earned ROE of 4.32% based upon a fully-adjusted test period. The proposed rates would provide for an earned ROE of 10.60% compared to the currently authorized ROE of 9.50%. This matter is pending.

Electric – Cost of Fuel

DESC’s retail electric rates include a cost of fuel component approved by the South Carolina Commission which may be adjusted periodically to reflect changes in the price of fuel purchased by DESC. In February 2024, DESC filed with the South Carolina Commission a proposal to decrease the total fuel cost component of retail electric rates. DESC’s proposed adjustment is designed to recover DESC’s current base fuel costs, including its existing under-collected balance, over the 12-month period beginning with the first billing cycle of May 2024. In addition, DESC proposed an increase to its variable environmental and avoided capacity cost component. The net effect is a proposed annual decrease of $315 million. In March 2024, DESC, the South Carolina Office of Regulatory Staff and another party of record filed a settlement agreement with the South Carolina Commission for approval to make certain adjustments to the February 2024 filing that would result in a net annual decrease of $316 million. In April 2024, the South Carolina Commission voted to approve the settlement agreement, with rates effective May 2024.

Electric - Transmission Project

In March 2024, DESC filed an application with the South Carolina Commission requesting approval of a CPCN to construct and operate the Church Creek - Charleston Transmission Line, comprised of a 7 mile 230 kV transmission line and associated facilities in Charleston County, South Carolina with an estimated total project cost of $40 million. This matter is pending.

Electric – Other

DESC has approval for a DSM rider through which it recovers expenditures related to its DSM programs. In January 2024, DESC filed an application with the South Carolina Commission seeking approval to recover $47 million of costs and net lost revenues associated with these programs, along with an incentive to invest in such programs. DESC requested that rates be effective with the first billing cycle of May 2024. In April 2024, the South Carolina Commission approved the request, effective with the first billing cycle of May 2024.

DESC utilizes a pension costs rider approved by the South Carolina Commission which is designed to allow recovery of projected pension costs, including under-collected balances or net of over-collected balances, as applicable. The rider is typically reviewed for adjustment every 12 months with any resulting increase or decrease going into effect beginning with the first billing cycle in May. In February 2024, DESC requested that the South Carolina Commission approve an adjustment to this rider to increase annual revenue by $9 million. In April 2024, the South Carolina Commission approved the request.

Regulatory Assets and Regulatory Liabilities

Rate-regulated utilities recognize in their financial statements certain revenues and expenses in different periods than do other enterprises. As a result, DESC has recorded regulatory assets and regulatory liabilities which are summarized in the following table. Except for NND Project costs and certain other unrecovered costs referenced herein, substantially all regulatory assets are either explicitly excluded from rate base or are effectively excluded from rate base due to their being offset by related liabilities.

	March 31,		December 31,
(millions)	2024		2023
Regulatory assets:
NND Project costs(1)	$	138	$	138
AROs(2)		38		44
Deferred employee benefit plan costs(3)		7		11
Other unrecovered plant(4)		19		19
DSM programs(5)		22		22
Cost of fuel and purchased gas under-collections(6)		71		154
Other		56		56
Regulatory assets - current		351		444
NND Project costs(1)		1,915		1,949
AROs(2)		382		379
Deferred employee benefit plan costs(3)		120		118
Interest rate hedges(7)		168		168
Other unrecovered plant(4)		70		66
DSM programs(5)		46		46
Environmental remediation costs(8)		33		34
Deferred storm damage costs(9)		39		40
Deferred transmission operating costs(10)		73		74
Derivatives(11)		99		103
Other(12)		149		130
Regulatory assets - noncurrent		3,094		3,107
Total regulatory assets	$	3,445	$	3,551
Regulatory liabilities:
Monetization of guaranty settlement(13)	$	67	$	67
Income taxes refundable through future rates(14)		37		37
Reserve for refunds to electric utility customers(15)		83		83
Derivatives(11)		15		12
Cost of fuel and purchased gas over-collections(6)		21		—
Other		10		6
Regulatory liabilities - current		233		205
Monetization of guaranty settlement(13)		619		635
Income taxes refundable through future rates(14)		830		839
Asset removal costs(16)		640		633
Reserve for refunds to electric utility customers(15)		212		237
Derivatives(11)		296		229
Other		1		6
Regulatory liabilities - noncurrent		2,598		2,579
Total regulatory liabilities	$	2,831	$	2,784

(1)Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

(2)Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years.

(3)Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. DESC expects to recover deferred pension costs through utility rates over periods through 2044. DESC expects to recover other deferred benefit costs through utility rates, primarily over average service periods of participating employees up to 11 years.

(4)Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2033. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized over five years related to the transition or conversion from coal to gas fired generation at certain facilities.

(5)Represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

(6)Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

(7)Represents the changes in fair value and payments made or received upon settlement of certain interest rate derivatives designated as cash flow hedges. The amounts recorded are expected to be amortized to interest expense over the lives of the underlying debt through 2065.

(8)Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

(9)Represents storm restoration costs for which DESC expects to receive future recovery through customer rates over approximately 10 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and are earning a current return.

(10)Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects recovery from customers through future rates over approximately 42 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and earning a current return. See Note 12 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

(11)Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

(12)Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

(13)Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

(14)Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years). See Note 7 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for additional information.

(15)Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

(16)Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

Regulatory assets have been recorded based on the probability of their recovery. All regulatory assets represent incurred costs that may be deferred under GAAP for regulated operations. The South Carolina Commission or FERC has reviewed and approved through specific orders certain of the items shown as regulatory assets. In addition, regulatory assets include, but are not limited to, certain costs which have not been specifically approved for recovery by one of these regulatory agencies. While such costs are not currently being recovered, management believes that they would be allowable under existing rate-making concepts embodied in rate orders or applicable state law and expects to recover these costs through rates in future periods.

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Revenue Recognition

3 Months Ended

Mar. 31, 2024

Revenue from Contract with Customer [Abstract]

Revenue Recognition

3. REVENUE RECOGNITION

DESC has disaggregated operating revenues by customer class as follows:

Three Months Ended March 31,	2024				2023
(millions)	Electric		Gas		Electric		Gas
Customer class:
Residential	$	283	$	117	$	262	$	109
Commercial		188		41		187		42
Industrial		87		18		91		22
Other		28		6		36		4
Revenues from contracts with customers		586		182		576		177
Other revenues		7		—		6		—
Total Operating Revenues	$	593	$	182	$	582	$	177

Contract liabilities represent the obligation to transfer goods or services to a customer for which consideration has already been received from the customer. DESC had contract liability balances of $6 million and $7 million at March 31, 2024 and December 31, 2023, respectively. During the three months ended March 31, 2024 and 2023, DESC recognized revenue of $3 million and $7 million, respectively, from the beginning contract liability balances as DESC fulfilled its obligations to provide service to its customers. Contract liabilities are recorded in customer deposits and customer prepayments in the Consolidated Balance Sheets.

Balances and activity related to contract costs deferred as regulatory assets were as follows:

	Regulatory Assets
(millions)	March 31, 2024		December 31, 2023
Beginning balance	$	11	$	9
Additional costs		—		3
Amortization		—		(1	)
Ending balance	$	11	$	11

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Equity

3 Months Ended

Mar. 31, 2024

Equity [Abstract]

Equity

4. EQUITY

For all periods presented, DESC’s authorized shares of common stock, no par value, were 50 million, of which 40.3 million were issued and outstanding, and DESC’s authorized shares of preferred stock, no par value, were 20 million, of which 1,000 shares were issued and outstanding. All outstanding shares of common and preferred stock are held by SCANA.

There have been no material changes to the dividend restrictions affecting DESC described in Note 5 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

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Long-Term and Short-Term Debt

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

Long-Term and Short-Term Debt

5. LONG-TERM AND SHORT-TERM DEBT

DESC’s short-term financing is supported through its access as co-borrower to Dominion Energy’s $6.0 billion joint revolving credit facility, which can be used for working capital, as support for the combined commercial paper programs of DESC, Dominion Energy, Virginia Power and Questar Gas, and for other general corporate purposes. Other than the items discussed below, there have been no significant changes from Note 6 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

At March 31, 2024, DESC’s share of commercial paper and letters of credit outstanding under its joint credit facility with Dominion Energy, was as follows:

(millions)	Maximum Facility Sub-Limit		Outstanding Commercial Paper		Outstanding Letters of Credit
Joint revolving credit facility(1)	$	1,000	$	210	$	—

(1)A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2024, the sub-limit for DESC was $500 million. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.

In 2023, FERC granted DESC authority through March 2025 to issue short-term indebtedness (pursuant to Section 204 of the Federal Power Act) in amounts not to exceed $2.2 billion outstanding with maturity dates of one year or less. At March 31, 2024, DESC had issued $210 million in commercial paper under its joint credit facility with Dominion Energy as disclosed above and had drawn on $371 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization. In addition, in 2023, FERC granted GENCO authority through March 2025 to issue short-term indebtedness not to exceed $200 million outstanding with maturity dates of one year or less. At March 31, 2024, GENCO had drawn on $23 million of its intercompany credit facility with Dominion Energy, as permitted by this FERC authorization.

DESC is obligated with respect to an aggregate of $68 million of industrial revenue bonds which are secured by letters of credit. These letters of credit expire, subject to renewal, in the fourth quarter of 2024.

DESC, GENCO and Fuel Company each have intercompany credit facilities with Dominion Energy with a maximum capacity of $900 million, $200 million and $400 million, respectively. At March 31, 2024 and December 31, 2023, DESC, GENCO and Fuel Company

collectively had borrowings outstanding under these agreements totaling $672 million and $442 million, respectively, which are recorded in affiliated and related party payables in DESC’s Consolidated Balance Sheets. Interest charges associated with these agreements were $10 million and $13 million for the three months ended March 31, 2024 and 2023, respectively.

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Income Taxes

3 Months Ended

Mar. 31, 2024

Income Tax Disclosure [Abstract]

Income Taxes

6. INCOME TAXES

For continuing operations, including noncontrolling interests, the statutory U.S. federal income tax rate reconciles to DESC’s effective income tax rate as follows:

Three Months Ended March 31,	2024			2023
U.S. statutory rate		21.0	%		21.0	%
Increases (reductions) resulting from:
State taxes, net of federal benefit		3.9			4.1
Reversal of excess deferred income taxes		(5.3	)		(4.7	)
Allowance for equity funds used during construction		(0.7	)		—
Settlements of uncertain tax positions		—			(9.9	)
Other, net		—			(0.1	)
Effective tax rate		18.9	%		10.4	%

As of March 31, 2024, there have been no material changes in DESC’s unrecognized tax benefits or possible changes that could reasonably be expected to occur during the next twelve months. See Note 7 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023, for a discussion of these unrecognized tax benefits.

For the three months ended March 31, 2023, DESC’s effective tax rate reflects an income tax benefit of $11 million from the effective settlement of a position that management believed was reasonably possible to occur.

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Derivative Financial Instruments

3 Months Ended

Mar. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

7. DERIVATIVE FINANCIAL INSTRUMENTS

DESC’s accounting policies, objectives, and strategies for using derivative instruments are discussed in Note 2 in the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023. See Note 8 for further information about fair value measurements and associated valuation methods for derivatives.

Cash collateral, as presented in the table below, is used to offset derivative assets and liabilities. Certain of DESC’s derivative instruments contain credit-related contingent provisions. These provisions require DESC to provide collateral upon the occurrence of specific events, primarily a credit rating downgrade. If the credit-related contingent features underlying the instruments that are in a liability position and not fully collateralized with cash were fully triggered as of March 31, 2024 and December 31, 2023, DESC would have been required to post $2 million and $4 million, respectively, of additional collateral to its counterparties. The collateral that would be required to be posted includes the impacts of any offsetting asset positions and any amounts already posted for derivatives and non-derivative contracts per contractual terms. DESC had not posted any collateral at March 31, 2024 and December 31, 2023 related to derivatives with credit-related contingent provisions that are in a liability position and not fully collateralized with cash. The aggregate fair value of all derivative instruments with credit-related contingent provisions that are in a liability position and not fully collateralized with cash as of March 31, 2024 and December 31, 2023 was $2 million and $4 million, respectively, which does not include the impact of any offsetting asset positions.

The table below presents derivative balances by type of financial instrument, if the gross amounts recognized in the Consolidated Balance Sheets were netted with derivative instruments and cash collateral received or paid:

	March 31, 2024								December 31, 2023
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts		Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts
Interest rate contracts:
Over-the-counter	$	1	$	—	$	—	$	1	$	—	$	—	$	—	$	—
Commodity contracts:
Over-the-counter		9		—		—		9		—		—		—		—
Total derivatives	$	10	$	—	$	—	$	10	$	—	$	—	$	—	$	—

(1)Excludes derivative assets of $245 million and $176 million at March 31, 2024 and December 31, 2023, respectively, which are not subject to master netting or similar arrangements.

	March 31, 2024								December 31, 2023
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts		Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	4	$	—	$	—	$	4
Total derivatives	$	2	$	—	$	—	$	2	$	4	$	—	$	—	$	4

(1)DESC did not have any derivative liabilities at March 31, 2024 and December 31, 2023, respectively, which were not subject to master netting or similar arrangements.

Volumes

The following table presents the volume of derivative activity at March 31, 2024. These volumes are based on open derivative positions and represent the combined absolute value of their long and short positions.

	Current		Noncurrent
Natural Gas (bcf):
Basis(1)		24		—
Electricity (MWh in millions):
Fixed price		2		23
Interest rate(2) (in millions)	$	—	$	71

(1)Includes options.

(2)Maturity is determined based on final settlement period.

Fair Value and Gains and Losses on Derivative Instruments

The following tables present the fair values of derivatives and where they are presented in the Consolidated Balance Sheets:

(millions)	Fair Value - Derivatives under Hedge Accounting		Fair Value - Derivatives not under Hedge Accounting		Total Fair Value
At March 31, 2024
ASSETS
Current Assets
Commodity	$	—	$	19	$	19
Total current derivative assets(1)		—		19		19
Noncurrent Assets
Commodity		—		235		235
Interest rate		—		1		1
Total noncurrent derivative assets(2)		—		236		236
Total derivative assets	$	—	$	255	$	255
LIABILITIES
Noncurrent Liabilities
Interest rate		—		2		2
Total noncurrent derivative liabilities(3)		—		2		2
Total derivative liabilities	$	—	$	2	$	2
At December 31, 2023
ASSETS
Current Assets
Commodity	$	—	$	9	$	9
Total current derivative assets(1)		—		9		9
Noncurrent Assets
Commodity		—		167		167
Interest rate		—		—		—
Total noncurrent derivative assets(2)		—		167		167
Total derivative assets	$	—	$	176	$	176
LIABILITIES
Noncurrent Liabilities
Interest rate		—		4		4
Total noncurrent derivative liabilities(3)		—		4		4
Total derivative liabilities	$	—	$	4	$	4

(1)Current derivative assets are presented in other current assets in DESC’s Consolidated Balance Sheets.

(2)Noncurrent derivative assets are presented in other deferred debits and other assets in DESC’s Consolidated Balance Sheets.

(3)Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in DESC’s Consolidated Balance Sheets.

The following tables present the gains and losses on derivatives, as well as where the associated activity is presented in the Consolidated Balance Sheets and Statements of Comprehensive Income:

Derivatives in Cash Flow Hedging Relationships

(millions)	Increase (Decrease) in Derivatives Subject to Regulatory Treatment(1)
Three Months Ended March 31,	2024		2023
Derivative type and location of gains (losses):
Interest rate	$	—	$	(1	)
Total	$	—	$	(1	)

(1)Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

Derivatives Not Designated as Hedging Instruments

(millions)	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
Three Months Ended March 31,	2024			2023
Derivative type and location of gains (losses):
Commodity:
Purchased power	$	(2	)	$	1
Interest rate:
Interest charges		(1	)		—
Total	$	(3	)	$	1

(1)Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Fair Value Measurements, Including Derivatives

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements, Including Derivatives

8. FAIR VALUE MEASUREMENTS, INCLUDING DERIVATIVES

DESC’s fair value measurements are made in accordance with the policies discussed in Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023. See Note 7 in this report for further information about DESC’s derivatives and hedge accounting activities.

The following table presents DESC’s quantitative information about Level 3 fair value measurements at March 31, 2024. The range and weighted average are presented in dollars for market price inputs and percentages for price volatility.

	Fair Value (millions)		Valuation Techniques	Unobservable Input		Range	Weighted Average(1)
Assets
Physical forwards:
Electricity	$	246	Discounted cash flow	Market price (per MWh)	(3)	24-102	51
Physical options:
Natural gas(2)	$	7	Option model	Market price (per Dth)	(3)	1-3	2
				Price volatility	(4)	10%-51%	34%
Total assets	$	253

(1)Averages weighted by volume.

(2)Includes basis.

(3)Represents market prices beyond defined terms for Levels 1 and 2.

(4)Represents volatilities unrepresented in published markets.

Sensitivity of the fair value measurements to changes in the significant unobservable inputs is as follows:

Significant Unobservable Inputs	Position	Change to Input	Impact on Fair Value Measurement
Market price	Buy	Increase (decrease)	Gain (loss)
Market price	Sell	Increase (decrease)	Loss (gain)
Price volatility	Buy	Increase (decrease)	Gain (loss)
Price volatility	Sell	Increase (decrease)	Loss (gain)

Recurring Fair Value Measurements

The following table presents DESC’s assets and liabilities that are measured at fair value on a recurring basis for each hierarchy level, including both current and noncurrent portions:

(millions)	Level 1		Level 2		Level 3		Total
At March 31, 2024
Assets
Commodity	$	—	$	1	$	253	$	254
Interest rate		—		1		—		1
Total assets	$	—	$	2	$	253	$	255
Liabilities
Interest rate	$	—	$	2	$	—	$	2
Total liabilities	$	—	$	2	$	—	$	2
At December 31, 2023
Assets
Commodity	$	—	$	—	$	176	$	176
Interest rate		—		—		—		—
Total assets	$	—	$	—	$	176	$	176
Liabilities
Interest rate	$	—	$	4	$	—	$	4
Total liabilities	$	—	$	4	$	—	$	4

The following table presents the net change in DESC’s assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

	Three Months Ended March 31,
	2024			2023
(millions)
Beginning balance	$	176		$	251
Total realized and unrealized gains (losses):
Included in earnings:
Purchased power		(2	)		1
Included in regulatory assets/liabilities		70			(63	)
Settlements		2			(1	)
Purchases		7			—
Ending balance	$	253		$	188

There are no unrealized gains and losses included in earnings in the Level 3 fair value category related to assets/liabilities still held at the reporting date for the three months ended March 31, 2024 and 2023.

Fair Value of Financial Instruments

Substantially all of DESC’s financial instruments are recorded at fair value, with the exception of the instruments described below, which are reported at historical cost. Estimated fair values have been determined using available market information and valuation methodologies considered appropriate by management. The carrying amount of financial instruments classified within current assets and current liabilities are representative of fair value because of the short-term nature of these instruments. For financial instruments that are not recorded at fair value, the carrying amounts and estimated fair values are as follows:

	March 31, 2024				December 31, 2023
(millions)	Carrying Amount		Estimated Fair Value(1)		Carrying Amount		Estimated Fair Value(1)
Long-term debt(2)	$	4,219	$	4,221	$	4,219	$	4,301
Affiliated long-term debt(3)		230		230		230		230

(1)Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

(2)Carrying amount includes current portions, if any, presented in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

(3)Carrying amount includes current portions presented in affiliated and related party payables.

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Employee Benefit Plans

3 Months Ended

Mar. 31, 2024

Retirement Benefits [Abstract]

Employee Benefit Plans

9. EMPLOYEE BENEFIT PLANS

In DESC’s Consolidated Statements of Comprehensive Income, the service cost component of net periodic benefit (credit) cost is reflected in other operations and maintenance expense with the non-service cost components reflected in other income. Components of net periodic benefit cost (credit) recorded by DESC were as follows:

(millions)	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2024			2023			2024			2023
Service cost	$	2		$	2		$	—		$	—
Interest cost		8			8			2			2
Expected return on assets		(9	)		(8	)		—			—
Amortization of actuarial losses		2			3			(1	)		(1	)
Net periodic benefit cost	$	3		$	5		$	1		$	1

During the three months ended March 31, 2024, DESC made no contributions to its pension trust. DESC expects to make $8 million of minimum required contributions to its qualified pension plan in 2024 and expects to receive reimbursement for such contributions from Santee Cooper. In April 2024, DESC made $1 million of contributions to its qualified pension plan. DESC recovers current pension costs through either a rate rider that may be adjusted annually for retail electric operations or through cost of service rates for gas operations.

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Commitments And Contingencies

3 Months Ended

Mar. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. COMMITMENTS AND CONTINGENCIES

As a result of issues generated in the ordinary course of business, DESC is involved in legal proceedings before various courts and is periodically subject to governmental examinations (including by regulatory authorities), inquiries and investigations. Certain legal proceedings and governmental examinations involve demands for unspecified amounts of damages, are in an initial procedural phase, involve uncertainty as to the outcome of pending appeals or motions, or involve significant factual issues that need to be resolved, such that it is not possible for DESC to estimate a range of possible loss. For such matters that DESC cannot estimate, a statement to this effect is made in the description of the matter. Other matters may have progressed sufficiently through the litigation or investigative processes such that DESC is able to estimate a range of possible loss. For legal proceedings and governmental examinations that DESC is able to reasonably estimate a range of possible losses, an estimated range of possible loss is provided, in excess of the accrued liability (if any) for such matters. DESC maintains various insurance programs, including general liability insurance coverage which provides coverage for personal injury or wrongful death cases. Any accrued liability is recorded on a gross basis with a receivable also recorded for any probable insurance recoveries. Estimated ranges of loss are inclusive of legal fees and net of any anticipated insurance recoveries. Any estimated range is based on currently available information and involves elements of judgment and significant uncertainties. Any estimated range of possible loss may not represent DESC’s maximum possible loss exposure. The circumstances of such legal proceedings and governmental examinations will change from time to time and actual results may vary significantly from the current estimate. For current proceedings not specifically reported below, management does not anticipate that the liabilities, if any, arising from such proceedings would have a material effect on DESC’s financial position, liquidity or results of operations. During the three months ended March 31, 2024, DESC recorded $6 million of charges in aggregate for various personal injury or wrongful death cases.

Environmental Matters

DESC is subject to costs resulting from a number of federal, state and local laws and regulations designed to protect human health and the environment. These laws and regulations affect future planning and existing operations. They can result in increased capital, operating and other costs as a result of compliance, remediation, containment and monitoring obligations.

From a regulatory perspective, DESC continually monitors and evaluates its current and projected emission levels and strives to comply with all state and federal regulations regarding those emissions. DESC participates in the SO2 and NOx emission allowance programs with respect to coal plant emissions and also has constructed additional pollution control equipment at its coal-fired electric generating plants. These actions are expected to address many of the rules and regulations discussed herein.

Air

The CAA, as amended, is a comprehensive program utilizing a broad range of regulatory tools to protect and preserve the nation’s air quality. At a minimum, states are required to establish regulatory programs to meet applicable requirements of the CAA. However, states may choose to develop regulatory programs that are more restrictive. Many of DESC’s facilities are subject to the CAA’s permitting and other requirements.

ACE Rule

In July 2019, the EPA published the final rule informally referred to as the ACE Rule, as a replacement for the Clean Power Plan. The ACE Rule regulated GHG emissions from existing coal-fired power plants pursuant to Section 111(d) of the CAA and required states to develop plans by July 2022 establishing unit-specific performance standards for existing coal-fired power plants. In January 2021, the U.S. Court of Appeals for the D.C. Circuit vacated the ACE Rule and remanded it to the EPA. This decision would take effect upon issuance of the court’s mandate. In March 2021, the court issued a partial mandate vacating and remanding all parts of the ACE Rule except for the portion of the ACE Rule that repealed the Clean Power Plan. In October 2021, the U.S. Supreme Court agreed to hear a challenge of the U.S. Court of Appeals for the D.C. Circuit’s decision on the ACE Rule. In June 2022, the U.S. Supreme Court reversed the D.C. Circuit’s decision on the ACE Rule and remanded the case back to the D.C. Circuit. In May 2023, the EPA proposed to repeal the ACE Rule as part of a package of proposed rules addressing CO2 emissions from new and existing fossil fuel-fired electric generating units. Until the EPA takes final action on this proposed rulemaking, DESC cannot predict an impact to its operations, financial condition and/or cash flows.

Carbon Regulations

In August 2016, the EPA issued a draft rule proposing to reaffirm that a source’s obligation to obtain a PSD or Title V permit for GHGs is triggered only if such permitting requirements are first triggered by non-GHG, or conventional, pollutants that are regulated by the New Source Review program, and exceed a significant emissions rate of 75,000 tons per year of CO2 equivalent emissions. Until the EPA ultimately takes final action on this rulemaking, DESC cannot predict the impact to its results of operations, financial condition and/or cash flows.

In December 2018, the EPA proposed revised Standards of Performance for Greenhouse Gas Emissions from New, Modified, and Reconstructed Stationary Sources. The proposed rule would amend the previous determination that the best system of emission reduction for newly constructed coal-fired steam generating units is no longer partial carbon capture and storage. Instead, the proposed revised best system of emission reduction for this source category is the most efficient demonstrated steam cycle (e.g., supercritical steam conditions for large units and subcritical steam conditions for small units) in combination with best operating practices. The proposed revision to the performance standards for coal-fired steam generating units remains pending. Until the EPA ultimately takes final action on this rulemaking, DESC cannot predict the impact to its results of operations, financial condition and/or cash flows.

Water

The CWA, as amended, is a comprehensive program requiring a broad range of regulatory tools including a permit program to authorize and regulate discharges to surface waters with strong enforcement mechanisms. DESC must comply with applicable aspects of the CWA programs at its operating facilities.

Regulation 316(b)

In October 2014, the final regulations under Section 316(b) of the CWA that govern existing facilities and new units at existing facilities that employ a cooling water intake structure and that have flow levels exceeding a minimum threshold became effective. The rule establishes a national standard for impingement based on seven compliance options, but forgoes the creation of a single technology standard for entrainment. Instead, the EPA has delegated entrainment technology decisions to state regulators. State regulators are to make case-by-case entrainment technology determinations after an examination of five mandatory facility-specific factors, including a social cost-benefit test, and six optional facility-specific factors. The rule governs all electric generating stations with water withdrawals above two MGD, with a heightened entrainment analysis for those facilities over 125 MGD. DESC has five facilities that are subject to the final regulations. DESC is also working with the EPA and state regulatory agencies to assess the applicability of Section 316(b) to five hydroelectric facilities. DESC anticipates that it may have to install impingement control technologies at certain of these stations that have once-through cooling systems. DESC is currently evaluating the need or potential for entrainment controls under the final rule as these decisions will be made on a case-by-case basis after a thorough review of detailed biological, technological, and cost benefit studies. DESC is conducting studies and implementing plans as required by the rule to determine appropriate intake structure modifications at certain facilities to ensure compliance with this rule. While the impacts of this rule could be material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Effluent Limitations Guidelines

In September 2015, the EPA released a final rule to revise the ELG Rule. The final rule established updated standards for wastewater discharges that apply primarily at coal and oil steam generating stations. Affected facilities are required to convert from wet to dry or closed cycle coal ash management, improve existing wastewater treatment systems and/or install new wastewater treatment technologies in order to meet the new discharge limits. In April 2017, the EPA granted two separate petitions for reconsideration of the final ELG Rule and stayed future compliance dates in the rule. Also in April 2017, the U.S. Court of Appeals for the Fifth Circuit granted the EPA’s request for a stay of the pending consolidated litigation challenging the rule while the EPA addresses the petitions

for reconsideration. In September 2017, the EPA signed a rule to postpone the earliest compliance dates for certain waste streams regulations in the final ELG Rule from November 2018 to November 2020; however, the latest date for compliance for these regulations was December 2023. In October 2020, the EPA released the final rule that extends the latest dates for compliance. Individual facilities’ compliance dates will vary based on circumstances and the determination by state regulators and may range from 2021 to 2028. While the impacts of this rule could be material to DESC’s results of operations, financial condition and/or cash flows, as DESC expects that wastewater treatment technology retrofits and modifications at the Williams and Wateree generating stations will be required, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Capacity Use Area

In November 2019, a new CUA was established in the counties surrounding the Cope Generating Station (Western Capacity Use Area) under the South Carolina Groundwater Use and Reporting Regulation. Under the regulation any groundwater well in a CUA that withdraws above three million gallons per month must be permitted. The Cope Generating Station is located within this new Western Capacity Use Area. Cope has been using four deep groundwater wells for cooling water and other house loads since 1996. Prior to designation of the new Western Capacity Use Area, the wells at Cope Station were only required to be registered not permitted. As a result of this designation, Cope will need to restore the surface water equipment to operable status to reduce reliance on groundwater wells. This includes completion of 316(b) requirements, (including SCDHEC BACT determination and modification of the station national pollutant discharge elimination system permit) and extensive inspection, repair and/or replacement of the associated surface water withdrawal equipment which has been idle since 1996. While the impacts of this rule change are potentially material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts for DESC.

Waste Management and Remediation

The operations of DESC are subject to a variety of state and federal laws and regulations governing the management and disposal of solid and hazardous waste, and release of hazardous substances associated with current and/or historical operations. The CERCLA, as amended, and similar state laws, may impose joint, several and strict liability for cleanup on potentially responsible parties who owned, operated or arranged for disposal at facilities affected by a release of hazardous substances. In addition, many states have created programs to incentivize voluntary remediation of sites where historical releases of hazardous substances are identified and property owners or responsible parties decide to initiate cleanups.

From time to time, DESC may be identified as a potentially responsible party in connection with the alleged release of hazardous substances or wastes at a site. Under applicable federal and state laws, DESC could be responsible for costs associated with the investigation or remediation of impacted sites, or subject to contribution claims by other responsible parties for their costs incurred at such sites. DESC also may identify, evaluate and remediate other potentially impacted sites under voluntary state programs. Remediation costs may be subject to reimbursement under DESC’s insurance policies, rate recovery mechanisms, or both. Except as described below, DESC does not believe these matters will have a material effect on results of operations, financial condition and/or cash flows.

DESC has four decommissioned manufactured gas plant sites in South Carolina that are in various states of investigation, remediation and monitoring under work plans approved by, or under review by, the SCDHEC or the EPA. In the fourth quarter of 2023, DESC completed the majority of remediation activities at one site. DESC anticipates the remaining activities at that site will be completed by 2025 at an estimated cost of $5 million, after which the site will continue to incur ongoing maintenance and monitoring obligations. DESC expects to recover costs arising from the remediation work at all four sites through rate recovery mechanisms and as of March 31, 2024, deferred amounts, net of amounts previously recovered through rates and insurance settlements, totaled $34 million and are included in regulatory assets.

Ash Pond and Landfill Closure Costs

In April 2015, the EPA enacted a final rule regulating CCR landfills, existing ash ponds that still receive and manage CCRs, and inactive ash ponds that do not receive, but still store, CCRs. DESC currently has inactive and existing CCR ponds and CCR landfills subject to the final rule at three different facilities. This rule created a legal obligation for DESC to retrofit or close all of its inactive and existing ash ponds over a certain period of time, as well as perform required monitoring, corrective action, and post-closure care activities as necessary.

In December 2016, legislation was enacted that creates a framework for EPA-approved state CCR permit programs. In August 2017, the EPA issued interim guidance outlining the framework for state CCR program approval. The EPA has enforcement authority until state programs are approved. The EPA and states with approved programs both will have authority to enforce CCR requirements under their respective rules and programs. In September 2017, the EPA agreed to reconsider portions of the CCR rule in response to two petitions for reconsideration. In March 2018, the EPA proposed certain changes to the CCR rule related to issues remanded as part of the pending litigation and other issues the EPA is reconsidering. Several of the proposed changes would allow states with approved CCR permit programs additional flexibility in implementing their programs. In July 2018, the EPA promulgated the first phase of changes to the CCR rule. In August 2018, the U.S. Court of Appeals for the D.C. Circuit issued its decision in the pending challenges

of the CCR rule, vacating and remanding to the EPA three provisions of the rule. Until this matter is resolved and all phases of the CCR rule are promulgated, DESC is unable to precisely estimate potential incremental impacts or costs related to existing coal ash sites in connection with future implementation of the final CCR rule. In May 2023, the EPA released a proposed rule addressing one of the previously remanded provisions of the CCR rule to regulate inactive surface impoundments located at retired generating stations that contained CCR and liquids after October 2015, and certain other inactive or previously closed surface impoundments, landfills or other areas that contain accumulations of CCR. Until the EPA ultimately takes final action on this rulemaking, DESC is unable to predict whether or to what extent the new rules will ultimately require additional controls. While such amounts may be material to DESC’s results of operations, financial condition and/or cash flows, the existing regulatory framework in South Carolina provides rate recovery mechanisms that could substantially mitigate any such impacts.

Claims and Litigation

The following describes certain legal proceedings involving DESC relating primarily to events occurring before closing of the SCANA Combination.

Matters Fully Resolved Prior to 2024 Impacting the Consolidated Financial Statements

Governmental Proceedings and Investigations

In June 2018, DESC received a notice of proposed assessment of approximately $410 million, excluding interest, from the SCDOR following its audit of DESC’s sales and use tax returns for the periods September 1, 2008 through December 31, 2017. The proposed assessment, which includes 100% of the NND Project, is based on the SCDOR’s position that DESC’s sales and use tax exemption for the NND Project does not apply because the facility will not become operational. In December 2020, the parties reached an agreement in principle in the amount of $165 million to resolve this matter. In June 2021, the parties executed a settlement agreement which allows DESC to fund the settlement amount through a combination of cash, shares of Dominion Energy common stock or real estate with an initial payment of at least $43 million in shares of Dominion Energy common stock. In August 2021, Dominion Energy issued 0.6 million shares of its common stock to satisfy DESC’s obligation for the initial payment under the settlement agreement. In May 2022, Dominion Energy issued an additional 0.9 million shares of its common stock to partially satisfy DESC’s remaining obligation under the settlement agreement. In June 2022, DESC requested approval from the South Carolina Commission to transfer certain real estate with a total settlement value of $51 million to satisfy its remaining obligation under the settlement agreement. In July 2022, the South Carolina Commission voted to approve the request and issued its final order in August 2022. In September 2022, DESC transferred certain non-utility property with a fair value of $28 million to the SCDOR under the settlement agreement. In December 2022, DESC transferred additional utility property with a fair value of $3 million to the SCDOR. In October 2022, DESC filed for approval to transfer the remaining real estate with FERC which was received in November 2022. In March 2023, DESC transferred utility property with a fair value of $10 million to the SCDOR resulting in a gain of $9 million ($7 million after-tax), recorded in other income, net in DESC’s Consolidated Statements of Comprehensive Income for the three months ended March 31, 2023. In June 2023, DESC transferred the remaining utility property with a fair value of $11 million to the SCDOR. In July 2023, DESC made a less than $1 million cash payment to the SCDOR to fully satisfy its remaining obligation, including applicable interest, under the settlement agreement.

Nuclear Operations

Other than the items discussed below, there have been no significant changes regarding DESC’s nuclear insurance and spent nuclear fuel as described in Note 12 to the Consolidated Financial Statements in the DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

During the first quarter of 2024, the total liability protection per nuclear incident available to all participants in the Secondary Financial Protection Program increased from $16.2 billion to $16.3 billion. This increase does not impact DESC’s responsibility per active unit under the Price-Anderson Amendments Act of 1988. Additionally, Dominion Energy increased the amount of coverage purchased from commercial insurance pools for Summer from $450 million to $500 million with the remainder provided through the mandatory industry retrospective rating plan.

Surety Bonds

At March 31, 2024, DESC had purchased $24 million of surety bonds. Under the terms of surety bonds, DESC is obligated to indemnify the respective surety bond company for any amounts paid.

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Operating Segments

3 Months Ended

Mar. 31, 2024

Segment Reporting [Abstract]

Operating Segments

11. OPERATING SEGMENTS

The Corporate and Other segment primarily includes specific items attributable to DESC’s operating segment that are not included in profit measures evaluated by executive management in assessing the segment’s performance or in allocating resources.

In the three months ended March 31, 2024 and 2023, DESC reported an insignificant amount of specific items in the Corporate and Other segment.

(millions)	External Revenue		Comprehensive Income (Loss) Available (Attributable) to Common Shareholder
Three Months Ended March 31, 2024
Dominion Energy South Carolina	$	775	$	75
Corporate and Other		—		(1	)
Consolidated total	$	775	$	74
Three Months Ended March 31, 2023
Dominion Energy South Carolina	$	759	$	86
Corporate and Other		—		6
Consolidated total	$	759	$	92

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Affiliated and Related Party Transactions

3 Months Ended

Mar. 31, 2024

Related Party Transactions [Abstract]

Affiliated and Related Party Transactions

12. AFFILIATED AND RELATED PARTY TRANSACTIONS

DES, on behalf of itself and its parent company, provides the following services to DESC, which are rendered at direct or allocated cost: information systems, telecommunications, customer support, marketing and sales, human resources, corporate compliance, purchasing, financial, risk management, public affairs, legal, investor relations, gas supply and capacity management, strategic planning, general administrative and retirement benefits. Costs for these services include amounts capitalized. Amounts expensed are primarily recorded in other operations and maintenance - affiliated suppliers and other income, net in the Consolidated Statements of Comprehensive Income.

DESC transacts with affiliates for certain quantities of electricity in the ordinary course of business. DESC also enters into certain commodity derivative contracts with affiliates. DESC uses these contracts, which are principally comprised of forward commodity purchases, to manage commodity price risks associated with purchases of electricity. See Note 7 for additional information.

	Three Months Ended March 31,
(millions)	2024		2023
Direct and allocated costs from DES(1)	$	53	$	57
Operating Revenues - Electric from sales to affiliate		1		1
Operating Expenses - Other taxes from affiliate		3		3
Purchases of electricity from solar affiliates		1		2

(1)Includes capitalized expenditures of $12 million and $16 million for the three months ended March 31, 2024 and 2023, respectively.

(millions)	March 31, 2024		December 31, 2023
Payable to DES		41		18
Payable to SCANA Corporation		7		7
Payable to Public Service Company of North Carolina, Incorporated		12		13
Derivative assets with affiliates(1)		42		33

(1)Includes amounts recorded in other current assets of $2 million as of both March 31, 2024 and December 31, 2023 and amounts recorded in other deferred debits and other assets of $40 million and $31 million as of March 31, 2024 and December 31, 2023, respectively.

Borrowings from an affiliate are described in Note 5.

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Other Income, Net

3 Months Ended

Mar. 31, 2024

Income Statement [Abstract]

Other Income, Net

13. OTHER INCOME, NET

Components of other income, net are as follows:

	Three Months Ended March 31,
(millions)	2024			2023
Other income	$	2		$	2
Gains on sales of assets(1)		1			10
Other expense		(5	)		(2	)
Allowance for equity funds used during construction		3			—
Other income, net	$	1		$	10

(1) Includes amounts recognized in 2023 in connection with the transfer of property to satisfy litigation. See Note 10 for additional information.

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Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2024

Accounting Policies [Abstract]

Basis of Consolidation and Variable Interest Entities

Basis of Consolidation and Variable Interest Entities

DESC has determined that it has a controlling financial interest in each of GENCO and Fuel Company (which are considered to be VIEs) and, accordingly, DESC’s Consolidated Financial Statements include, after eliminating intercompany balances and transactions, the accounts of DESC, GENCO and Fuel Company. See Note 2 to the Consolidated Financial Statements included in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for a description of GENCO and Fuel Company.

DESC purchases shared services from DES, an affiliated VIE that provides accounting, legal, finance and certain administrative and technical services to all Dominion Energy subsidiaries, including DESC. DESC has determined that it is not the primary beneficiary of DES as it does not have either the power to direct the activities that most significantly impact its economic performance or an obligation to absorb losses and benefits which could be significant to it. See Note 12 for amounts attributable to affiliates.

Significant Accounting Policies

There have been no significant changes from Note 2 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023, except as follows.

New Accounting Standards

New Accounting Standards

Climate-Related Disclosures

In March 2024, the SEC issued guidance for climate-related disclosures. The guidance requires disclosure of the financial statement impacts of severe weather events and other natural conditions, including amounts capitalized or expensed as well as any associated recoveries. In addition, the guidance requires disclosure of amounts related to renewable energy credits or carbon offsets if utilized as a material component of plans to achieve climate-related targets or goals. This guidance, which is currently subject to a stay issued by the SEC, would be effective for the fiscal year beginning January 1, 2025. DESC expects this guidance to only impact its disclosures with no impacts to its results of operations, cash flows or financial condition.

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Rate and Other Regulatory Matters (Tables)

3 Months Ended

Mar. 31, 2024

Regulated Operations [Abstract]

Schedule of Regulatory Assets and Liabilities

	March 31,		December 31,
(millions)	2024		2023
Regulatory assets:
NND Project costs(1)	$	138	$	138
AROs(2)		38		44
Deferred employee benefit plan costs(3)		7		11
Other unrecovered plant(4)		19		19
DSM programs(5)		22		22
Cost of fuel and purchased gas under-collections(6)		71		154
Other		56		56
Regulatory assets - current		351		444
NND Project costs(1)		1,915		1,949
AROs(2)		382		379
Deferred employee benefit plan costs(3)		120		118
Interest rate hedges(7)		168		168
Other unrecovered plant(4)		70		66
DSM programs(5)		46		46
Environmental remediation costs(8)		33		34
Deferred storm damage costs(9)		39		40
Deferred transmission operating costs(10)		73		74
Derivatives(11)		99		103
Other(12)		149		130
Regulatory assets - noncurrent		3,094		3,107
Total regulatory assets	$	3,445	$	3,551
Regulatory liabilities:
Monetization of guaranty settlement(13)	$	67	$	67
Income taxes refundable through future rates(14)		37		37
Reserve for refunds to electric utility customers(15)		83		83
Derivatives(11)		15		12
Cost of fuel and purchased gas over-collections(6)		21		—
Other		10		6
Regulatory liabilities - current		233		205
Monetization of guaranty settlement(13)		619		635
Income taxes refundable through future rates(14)		830		839
Asset removal costs(16)		640		633
Reserve for refunds to electric utility customers(15)		212		237
Derivatives(11)		296		229
Other		1		6
Regulatory liabilities - noncurrent		2,598		2,579
Total regulatory liabilities	$	2,831	$	2,784

(1)Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

(2)Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years.

(3)Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. DESC expects to recover deferred pension costs through utility rates over periods through 2044. DESC expects to recover other deferred benefit costs through utility rates, primarily over average service periods of participating employees up to 11 years.

(4)Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2033. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized over five years related to the transition or conversion from coal to gas fired generation at certain facilities.

(5)Represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

(6)Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

(7)Represents the changes in fair value and payments made or received upon settlement of certain interest rate derivatives designated as cash flow hedges. The amounts recorded are expected to be amortized to interest expense over the lives of the underlying debt through 2065.

(8)Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

(9)Represents storm restoration costs for which DESC expects to receive future recovery through customer rates over approximately 10 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and are earning a current return.

(10)Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects recovery from customers through future rates over approximately 42 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and earning a current return. See Note 12 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

(11)Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

(12)Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

(13)Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

(14)Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years). See Note 7 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for additional information.

(15)Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

(16)Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

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Revenue Recognition (Tables)

3 Months Ended

Mar. 31, 2024

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

DESC has disaggregated operating revenues by customer class as follows:

Three Months Ended March 31,	2024				2023
(millions)	Electric		Gas		Electric		Gas
Customer class:
Residential	$	283	$	117	$	262	$	109
Commercial		188		41		187		42
Industrial		87		18		91		22
Other		28		6		36		4
Revenues from contracts with customers		586		182		576		177
Other revenues		7		—		6		—
Total Operating Revenues	$	593	$	182	$	582	$	177

Balance and Activity Related to Contract Costs Deferred as Regulatory Assets

Balances and activity related to contract costs deferred as regulatory assets were as follows:

	Regulatory Assets
(millions)	March 31, 2024		December 31, 2023
Beginning balance	$	11	$	9
Additional costs		—		3
Amortization		—		(1	)
Ending balance	$	11	$	11

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Long-Term and Short-Term Debt (Tables)

3 Months Ended

Mar. 31, 2024

Debt Disclosure [Abstract]

Schedule of Line of Credit Facilities

At March 31, 2024, DESC’s share of commercial paper and letters of credit outstanding under its joint credit facility with Dominion Energy, was as follows:

(millions)	Maximum Facility Sub-Limit		Outstanding Commercial Paper		Outstanding Letters of Credit
Joint revolving credit facility(1)	$	1,000	$	210	$	—

(1)A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2024, the sub-limit for DESC was $500 million. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Income Taxes (Tables)

3 Months Ended

Mar. 31, 2024

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

Three Months Ended March 31,	2024			2023
U.S. statutory rate		21.0	%		21.0	%
Increases (reductions) resulting from:
State taxes, net of federal benefit		3.9			4.1
Reversal of excess deferred income taxes		(5.3	)		(4.7	)
Allowance for equity funds used during construction		(0.7	)		—
Settlements of uncertain tax positions		—			(9.9	)
Other, net		—			(0.1	)
Effective tax rate		18.9	%		10.4	%

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Derivative Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2024

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Offsetting Assets

The table below presents derivative balances by type of financial instrument, if the gross amounts recognized in the Consolidated Balance Sheets were netted with derivative instruments and cash collateral received or paid:

	March 31, 2024								December 31, 2023
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts		Gross Assets Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Received		Net Amounts
Interest rate contracts:
Over-the-counter	$	1	$	—	$	—	$	1	$	—	$	—	$	—	$	—
Commodity contracts:
Over-the-counter		9		—		—		9		—		—		—		—
Total derivatives	$	10	$	—	$	—	$	10	$	—	$	—	$	—	$	—

(1)Excludes derivative assets of $245 million and $176 million at March 31, 2024 and December 31, 2023, respectively, which are not subject to master netting or similar arrangements.

Offsetting Liabilities

	March 31, 2024								December 31, 2023
	Gross Amounts Not Offset in the Consolidated Balance Sheet								Gross Amounts Not Offset in the Consolidated Balance Sheet
(millions)	Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts		Gross Liabilities Presented in the Consolidated Balance Sheet(1)		Financial Instruments		Cash Collateral Paid		Net Amounts
Interest rate contracts:
Over-the-counter	$	2	$	—	$	—	$	2	$	4	$	—	$	—	$	4
Total derivatives	$	2	$	—	$	—	$	2	$	4	$	—	$	—	$	4

(1)DESC did not have any derivative liabilities at March 31, 2024 and December 31, 2023, respectively, which were not subject to master netting or similar arrangements.

Schedule of Volume of Derivative Activity

The following table presents the volume of derivative activity at March 31, 2024. These volumes are based on open derivative positions and represent the combined absolute value of their long and short positions.

	Current		Noncurrent
Natural Gas (bcf):
Basis(1)		24		—
Electricity (MWh in millions):
Fixed price		2		23
Interest rate(2) (in millions)	$	—	$	71

(1)Includes options.

(2)Maturity is determined based on final settlement period.

Fair Value of Derivatives

The following tables present the fair values of derivatives and where they are presented in the Consolidated Balance Sheets:

(millions)	Fair Value - Derivatives under Hedge Accounting		Fair Value - Derivatives not under Hedge Accounting		Total Fair Value
At March 31, 2024
ASSETS
Current Assets
Commodity	$	—	$	19	$	19
Total current derivative assets(1)		—		19		19
Noncurrent Assets
Commodity		—		235		235
Interest rate		—		1		1
Total noncurrent derivative assets(2)		—		236		236
Total derivative assets	$	—	$	255	$	255
LIABILITIES
Noncurrent Liabilities
Interest rate		—		2		2
Total noncurrent derivative liabilities(3)		—		2		2
Total derivative liabilities	$	—	$	2	$	2
At December 31, 2023
ASSETS
Current Assets
Commodity	$	—	$	9	$	9
Total current derivative assets(1)		—		9		9
Noncurrent Assets
Commodity		—		167		167
Interest rate		—		—		—
Total noncurrent derivative assets(2)		—		167		167
Total derivative assets	$	—	$	176	$	176
LIABILITIES
Noncurrent Liabilities
Interest rate		—		4		4
Total noncurrent derivative liabilities(3)		—		4		4
Total derivative liabilities	$	—	$	4	$	4

(1)Current derivative assets are presented in other current assets in DESC’s Consolidated Balance Sheets.

(2)Noncurrent derivative assets are presented in other deferred debits and other assets in DESC’s Consolidated Balance Sheets.

(3)Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in DESC’s Consolidated Balance Sheets.

Derivatives in Cash Flow Hedging Relationships

The following tables present the gains and losses on derivatives, as well as where the associated activity is presented in the Consolidated Balance Sheets and Statements of Comprehensive Income:

Derivatives in Cash Flow Hedging Relationships

(millions)	Increase (Decrease) in Derivatives Subject to Regulatory Treatment(1)
Three Months Ended March 31,	2024		2023
Derivative type and location of gains (losses):
Interest rate	$	—	$	(1	)
Total	$	—	$	(1	)

(1)Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

Derivatives Not Designated as Hedging Instruments

Derivatives Not Designated as Hedging Instruments

(millions)	Amount of Gain (Loss) Recognized in Income on Derivatives(1)
Three Months Ended March 31,	2024			2023
Derivative type and location of gains (losses):
Commodity:
Purchased power	$	(2	)	$	1
Interest rate:
Interest charges		(1	)		—
Total	$	(3	)	$	1

(1)Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Fair Value Measurements, Including Derivatives (Tables)

3 Months Ended

Mar. 31, 2024

Fair Value Disclosures [Abstract]

Schedule of Quantitative Information About Level 3 Fair Value Measurements

The following table presents DESC’s quantitative information about Level 3 fair value measurements at March 31, 2024. The range and weighted average are presented in dollars for market price inputs and percentages for price volatility.

	Fair Value (millions)		Valuation Techniques	Unobservable Input		Range	Weighted Average(1)
Assets
Physical forwards:
Electricity	$	246	Discounted cash flow	Market price (per MWh)	(3)	24-102	51
Physical options:
Natural gas(2)	$	7	Option model	Market price (per Dth)	(3)	1-3	2
				Price volatility	(4)	10%-51%	34%
Total assets	$	253

(1)Averages weighted by volume.

(2)Includes basis.

(3)Represents market prices beyond defined terms for Levels 1 and 2.

(4)Represents volatilities unrepresented in published markets.

Schedule of Sensitivity of The Fair Value Measurements To Changes in The Significant Unobservable Inputs

Sensitivity of the fair value measurements to changes in the significant unobservable inputs is as follows:

Significant Unobservable Inputs	Position	Change to Input	Impact on Fair Value Measurement
Market price	Buy	Increase (decrease)	Gain (loss)
Market price	Sell	Increase (decrease)	Loss (gain)
Price volatility	Buy	Increase (decrease)	Gain (loss)
Price volatility	Sell	Increase (decrease)	Loss (gain)

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents DESC’s assets and liabilities that are measured at fair value on a recurring basis for each hierarchy level, including both current and noncurrent portions:

(millions)	Level 1		Level 2		Level 3		Total
At March 31, 2024
Assets
Commodity	$	—	$	1	$	253	$	254
Interest rate		—		1		—		1
Total assets	$	—	$	2	$	253	$	255
Liabilities
Interest rate	$	—	$	2	$	—	$	2
Total liabilities	$	—	$	2	$	—	$	2
At December 31, 2023
Assets
Commodity	$	—	$	—	$	176	$	176
Interest rate		—		—		—		—
Total assets	$	—	$	—	$	176	$	176
Liabilities
Interest rate	$	—	$	4	$	—	$	4
Total liabilities	$	—	$	4	$	—	$	4

Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis and included in Level 3

The following table presents the net change in DESC’s assets and liabilities measured at fair value on a recurring basis and included in the Level 3 fair value category.

	Three Months Ended March 31,
	2024			2023
(millions)
Beginning balance	$	176		$	251
Total realized and unrealized gains (losses):
Included in earnings:
Purchased power		(2	)		1
Included in regulatory assets/liabilities		70			(63	)
Settlements		2			(1	)
Purchases		7			—
Ending balance	$	253		$	188

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments

For financial instruments that are not recorded at fair value, the carrying amounts and estimated fair values are as follows:

	March 31, 2024				December 31, 2023
(millions)	Carrying Amount		Estimated Fair Value(1)		Carrying Amount		Estimated Fair Value(1)
Long-term debt(2)	$	4,219	$	4,221	$	4,219	$	4,301
Affiliated long-term debt(3)		230		230		230		230

(1)Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

(2)Carrying amount includes current portions, if any, presented in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

(3)Carrying amount includes current portions presented in affiliated and related party payables.

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Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2024

Retirement Benefits [Abstract]

Components of Net Periodic Benefit Cost (Credit)

(millions)	Pension Benefits						Other Postretirement Benefits
Three Months Ended March 31,	2024			2023			2024			2023
Service cost	$	2		$	2		$	—		$	—
Interest cost		8			8			2			2
Expected return on assets		(9	)		(8	)		—			—
Amortization of actuarial losses		2			3			(1	)		(1	)
Net periodic benefit cost	$	3		$	5		$	1		$	1

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Operating Segments (Tables)

3 Months Ended

Mar. 31, 2024

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

(millions)	External Revenue		Comprehensive Income (Loss) Available (Attributable) to Common Shareholder
Three Months Ended March 31, 2024
Dominion Energy South Carolina	$	775	$	75
Corporate and Other		—		(1	)
Consolidated total	$	775	$	74
Three Months Ended March 31, 2023
Dominion Energy South Carolina	$	759	$	86
Corporate and Other		—		6
Consolidated total	$	759	$	92

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Affiliated and Related Party Transactions (Tables)

3 Months Ended

Mar. 31, 2024

Related Party Transactions [Abstract]

Schedule of Affiliated Transactions

Amounts expensed are primarily recorded in other operations and maintenance - affiliated suppliers and other income, net in the Consolidated Statements of Comprehensive Income.

	Three Months Ended March 31,
(millions)	2024		2023
Direct and allocated costs from DES(1)	$	53	$	57
Operating Revenues - Electric from sales to affiliate		1		1
Operating Expenses - Other taxes from affiliate		3		3
Purchases of electricity from solar affiliates		1		2

(1)Includes capitalized expenditures of $12 million and $16 million for the three months ended March 31, 2024 and 2023, respectively.

Schedule of Affiliated Transactions

(millions)	March 31, 2024		December 31, 2023
Payable to DES		41		18
Payable to SCANA Corporation		7		7
Payable to Public Service Company of North Carolina, Incorporated		12		13
Derivative assets with affiliates(1)		42		33

(1)Includes amounts recorded in other current assets of $2 million as of both March 31, 2024 and December 31, 2023 and amounts recorded in other deferred debits and other assets of $40 million and $31 million as of March 31, 2024 and December 31, 2023, respectively.

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Other Income, Net (Tables)

3 Months Ended

Mar. 31, 2024

Income Statement [Abstract]

Components of Other Income, Net

Components of other income, net are as follows:

	Three Months Ended March 31,
(millions)	2024			2023
Other income	$	2		$	2
Gains on sales of assets(1)		1			10
Other expense		(5	)		(2	)
Allowance for equity funds used during construction		3			—
Other income, net	$	1		$	10

(1) Includes amounts recognized in 2023 in connection with the transfer of property to satisfy litigation. See Note 10 for additional information.

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Rate and Other Regulatory Matters (Narrative) (Detail) $ in Millions	1 Months Ended			3 Months Ended
	Mar. 31, 2024 USD ($) mi kV	Feb. 29, 2024 USD ($)	Jan. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)
Rate And Other Regulatory Matters [Line Items]
Miles of Lines | mi	7
Type of Line | kV	230
Estimated electric transmission project cost	$ 40
Regulatory asset recovery assessment end period				2078
Dominion Energy South Carolina, Inc. [Member]
Rate And Other Regulatory Matters [Line Items]
Storm restoration recovery period				10 years
Electric Base Rate Case [Member]
Rate And Other Regulatory Matters [Line Items]
Amount of Increase in proposed non fuel base rate	295
Decrease in storm damage and DSM components	4
Increase in proposed base rate amount	$ 291
Increase in proposed base rate percentage	12.59%
Percentage of current authorized earned ROE	9.50%
Percentage of earned return on equity	4.32%
Percentage of earned return on equity proposed rate	0.60%
Electric - Cost of Fuel [Member]
Rate And Other Regulatory Matters [Line Items]
Proposed South Carolina Commission Order for Decrease of Total Fuel Cost Component of Retail Electric Rates to produce a projected under-recovery		$ 315
South Carolina Commission Order for Increase/Decrease of Total Fuel Cost Component of Retail Electric Rates to produce a projected under-recovery	$ 316			$ 316
Reserve For Refunds To Electric Utility Customers [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period				11 years
Deferred Losses or Gains On Interest Rate Derivatives [Member]
Rate And Other Regulatory Matters [Line Items]
Changes in fair value and payments of interest rate derivatives designated as cash flow hedge, amortized to interest expense, year				2065
Monetization Of Guaranty Settlement [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period				20 years
End period for recovery				Dec. 31, 2039
Income Taxes Refundable Through Future Rates [Member]
Rate And Other Regulatory Matters [Line Items]
Remaining lives of related property period				85 years
NND Project Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period				20 years
End period for recovery				Dec. 31, 2039
Deferred Employee Benefit Plan Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Regulatory asset recovery assessment end period				2044
Average service period expected to recover other deferred benefit costs				11 years
Other Unrecovered Plant [Member]
Rate And Other Regulatory Matters [Line Items]
Amortization of carrying value of coal-fired generating unit				2025
New expected amortization of carrying value of coal-fired generating unit				2033
Advanced Metering Infrastructure Project [Member]
Rate And Other Regulatory Matters [Line Items]
New expected amortization of carrying value of coal-fired generating unit				2028
Demand Side Management Programs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	3 years			3 years
Asset Retirement Obligation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	105 years			105 years
Environmental Remediation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	24 years			24 years
Deferred Transmission Operating Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset	42 years			42 years
Rider D S M [Member] | Electric - Other [Member]
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount			$ 47
South Carolina Commission [Member] | Electric - Other [Member]
Rate And Other Regulatory Matters [Line Items]
Annual increase (decrease) in pension cost rider		$ 9

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Rate and Other Regulatory Matters (Schedule of Regulatory Assets) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Regulatory Assets
Regulatory assets, current		$ 351	$ 444
Regulatory assets, noncurrent		3,094	3,107
Total regulatory assets		3,445	3,551
NND Project Costs [Member]
Regulatory Assets
Regulatory assets, current	[1]	138	138
Regulatory assets, noncurrent	[1]	1,915	1,949
Deferred Employee Benefit Plan Costs [Member]
Regulatory Assets
Regulatory assets, current	[2]	7	11
Regulatory assets, noncurrent	[2]	120	118
Interest Rate Hedges [Member]
Regulatory Assets
Regulatory assets, noncurrent	[3]	168	168
Other Unrecovered Plant [Member]
Regulatory Assets
Regulatory assets, current	[4]	19	19
Regulatory assets, noncurrent	[4]	70	66
Demand Side Management Programs [Member]
Regulatory Assets
Regulatory assets, current	[5]	22	22
Regulatory assets, noncurrent	[5]	46	46
Other Regulatory Assets [Member]
Regulatory Assets
Regulatory assets, current		56	56
Regulatory assets, noncurrent	[6]	149	130
Cost of Fuel and Purchased Gas Under-Collections [Member]
Regulatory Assets
Regulatory assets, current	[7]	71	154
Asset Retirement Obligation Costs [Member]
Regulatory Assets
Regulatory assets, current	[8]	38	44
Regulatory assets, noncurrent	[8]	382	379
Environmental Remediation Costs [Member]
Regulatory Assets
Regulatory assets, noncurrent	[9]	33	34
Deferred Storm Damage Costs [Member]
Regulatory Assets
Regulatory assets, noncurrent	[10]	39	40
Deferred Transmission Operating Costs [Member]
Regulatory Assets
Regulatory assets, noncurrent	[11]	73	74
Derivative [Member]
Regulatory Assets
Regulatory assets, noncurrent	[12]	$ 99	$ 103

[1] Reflects expenditures associated with the NND Project, which pursuant to the SCANA Merger Approval Order, will be recovered from electric service customers over a 20-year period ending in 2039.

[2] Employee benefit plan costs have historically been recovered as they have been recorded under GAAP. Deferred employee benefit plan costs represent amounts of pension and other postretirement benefit costs which were accrued as liabilities and treated as regulatory assets pursuant to FERC guidance, and costs deferred pursuant to specific South Carolina Commission regulatory orders. DESC expects to recover deferred pension costs through utility rates over periods through 2044. DESC expects to recover other deferred benefit costs through utility rates, primarily over average service periods of participating employees up to 11 years.

[3] Represents the changes in fair value and payments made or received upon settlement of certain interest rate derivatives designated as cash flow hedges. The amounts recorded are expected to be amortized to interest expense over the lives of the underlying debt through 2065.

[4] Represents the carrying value of coal-fired generating units, including related materials and supplies inventory, retired from service prior to being fully depreciated. DESC is amortizing these amounts through cost of service rates following depreciation amounts that were designed to recover the retired units cost over their previous estimated remaining useful lives, which has been estimated to be through 2025. Based on current projections of remaining decommissioning costs, projected recovery is expected to extend through 2033. In addition, amounts include unrecovered costs of existing meters and equipment retired from service prior to being fully depreciated as part of the Advanced Metering Infrastructure project, which are being recovered through rates through 2028. This amount also includes certain inventory and preliminary survey and investigation charges being amortized over five years related to the transition or conversion from coal to gas fired generation at certain facilities.

[5] Represents deferred costs associated with electric demand reduction programs, and such deferred costs are currently being recovered over three years through an approved rate rider.

[6] Various other regulatory assets are expected to be recovered through rates over varying periods through 2078.

[7] Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

[8] Represents uncollected costs, including deferred depreciation and accretion expense, related to legal obligations associated with the future retirement of generation, transmission and distribution properties. The AROs primarily relate to DESC’s electric generating facilities, including Summer, and are expected to be recovered over the related property lives and periods of decommissioning which may range up to approximately 105 years.

[9] Reflects amounts associated with the assessment and clean-up of sites currently or formerly owned by DESC. Such remediation costs are expected to be recovered over periods of up to 24 years. See Note 10 for additional information.

[10] Represents storm restoration costs for which DESC expects to receive future recovery through customer rates over approximately 10 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and are earning a current return.

[11] Includes deferred depreciation and property taxes associated with certain transmission assets for which DESC expects recovery from customers through future rates over approximately 42 years pursuant to the settlement agreement approved in DESC’s retail electric base rate case. Unamortized amounts are included in rate base and earning a current return. See Note 12 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023.

[12] Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

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Rate and Other Regulatory Matters (Schedule of Regulatory Liabilities) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Regulatory Liabilities
Regulatory liability, current		$ 233	$ 205
Regulatory liability, noncurrent		2,598	2,579
Total regulatory liabilities		2,831	2,784
Monetization Of Guaranty Settlement [Member]
Regulatory Liabilities
Regulatory liability, current	[1]	67	67
Regulatory liability, noncurrent	[1]	619	635
Income Taxes Refundable Through Future Rates [Member]
Regulatory Liabilities
Regulatory liability, current	[2]	37	37
Regulatory liability, noncurrent	[2]	830	839
Reserve For Refunds To Electric Utility Customers [Member]
Regulatory Liabilities
Regulatory liability, current	[3]	83	83
Regulatory liability, noncurrent	[3]	212	237
Cost of Fuel and Purchased Gas Under-Collections [Member]
Regulatory Liabilities
Regulatory liability, current	[4]	21
Other Regulatory Liability [Member]
Regulatory Liabilities
Regulatory liability, current		10	6
Regulatory liability, noncurrent		1	6
Asset Removal Costs [Member]
Regulatory Liabilities
Regulatory liability, noncurrent	[5]	640	633
Derivative [Member]
Regulatory Liabilities
Regulatory liability, current	[6]	15	12
Regulatory liability, noncurrent	[6]	$ 296	$ 229

[1] Represents proceeds related to the monetization of the Toshiba Settlement. In accordance with the SCANA Merger Approval Order, this balance, net of amounts that may be required to satisfy liens, will be refunded to electric customers over a 20-year period ending in 2039.

[2] Includes (i) excess deferred income taxes arising from the remeasurement of deferred income taxes in connection with the enactment of the 2017 Tax Reform Act (certain of which are protected under normalization rules and will be amortized over the remaining lives of related property, and certain of which will be amortized to the benefit of customers over prescribed periods as instructed by regulators) and (ii) deferred income taxes arising from investment tax credits, offset by (iii) deferred income taxes that arise from utility operations that have not been included in customer rates (a portion of which relate to depreciation and are expected to be recovered over the remaining lives of the related property which may range up to 85 years). See Note 7 to the Consolidated Financial Statements in DESC’s Annual Report on Form 10-K for the year ended December 31, 2023 for additional information.

[3] Reflects amounts previously collected from retail electric customers of DESC for the NND Project to be credited to customers over an estimated 11-year period effective February 2019 in connection with the SCANA Merger Approval Order.

[4] Represents amounts under- or over-collected from customers pursuant to the cost of fuel and purchased gas components approved by the South Carolina Commission.

[5] Represents estimated net collections through depreciation rates of amounts to be expended for the removal of assets in the future.

[6] Represents changes in the fair value of derivatives, excluding separately presented interest rate hedges, that following settlement are expected to be recovered from or refunded to customers.

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Revenue Recognition (Disaggregation of Revenue) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Total Operating Revenues	[1]	$ 775	$ 759
Electric Operations
Operating revenue from contracts with customers		586	576
Other revenues		7	6
Total Operating Revenues		593	582
Gas Distribution
Operating revenue from contracts with customers		182	177
Other revenues		0	0
Total Operating Revenues		182	177
Residential | Electric Operations
Operating revenue from contracts with customers		283	262
Residential | Gas Distribution
Operating revenue from contracts with customers		117	109
Commercial | Electric Operations
Operating revenue from contracts with customers		188	187
Commercial | Gas Distribution
Operating revenue from contracts with customers		41	42
Industrial | Electric Operations
Operating revenue from contracts with customers		87	91
Industrial | Gas Distribution
Operating revenue from contracts with customers		18	22
Other | Electric Operations
Operating revenue from contracts with customers		28	36
Other | Gas Distribution
Operating revenue from contracts with customers		$ 6	$ 4

[1] See Note 12 for amounts attributable to affiliates.

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Revenue Recognition (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Contract liability balances	$ 6		$ 7
Revenue recognized from contract liability balances	$ 3	$ 7

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Revenue Recognition (Balance and Activity Related to Contract Costs Deferred as Regulatory Assets) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Revenues [Abstract]
Beginning balance	$ 11	$ 9
Additional costs	0	3
Amortization	0	(1)
Ending balance	$ 11	$ 11

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Equity (Narrative) (Detail) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Class Of Stock [Line Items]
Common stock, par value
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	40,300,000	40,300,000
Common stock, shares outstanding	40,300,000	40,300,000
Preferred stock, par value
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	1,000	1,000
Preferred stock, shares outstanding	1,000	1,000

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Long-Term and Short-Term Debt (Narrative) (Detail) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Sep. 30, 2023
Debt Instrument [Line Items]
Commercial paper borrowing limit				$ 2,200,000,000
Affiliated and related party payables and other		$ 133,000,000		$ 166,000,000
Interest charges	[1]	67,000,000	$ 59,000,000
Maximum [Member]
Debt Instrument [Line Items]
Short term commercial paper maturity period				1 year
Genco
Debt Instrument [Line Items]
Commercial paper borrowing limit				$ 200,000,000
Genco | Maximum [Member]
Debt Instrument [Line Items]
Short term commercial paper maturity period				1 year
Dominion Energy
Debt Instrument [Line Items]
Affiliated and related party payables and other		672,000,000		$ 442,000,000
Interest charges		10,000,000	$ 13,000,000
Inter company credit facility maximum capacity		900,000,000
Dominion Energy | Genco
Debt Instrument [Line Items]
Inter company credit facility maximum capacity		200,000,000
Dominion Energy | Fuel company
Debt Instrument [Line Items]
Inter company credit facility maximum capacity		400,000,000
Joint Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	[2]	1,000,000,000
Joint Revolving Credit Facility | Commercial Paper
Debt Instrument [Line Items]
Debt instrument, face amount		210,000,000
Joint Revolving Credit Facility | Dominion Energy
Debt Instrument [Line Items]
Maximum Facility Sub-Limit					$ 6,000,000,000
Industrial Revenue Bonds
Debt Instrument [Line Items]
Debt instrument, face amount		68,000,000		$ 68,000,000
Intercompany Credit Facility
Debt Instrument [Line Items]
Line of credit, outstanding		371,000,000
Intercompany Credit Facility | Genco
Debt Instrument [Line Items]
Line of credit, outstanding		$ 23,000,000

[1] See Note 12 for amounts attributable to affiliates.

[2] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2024, the sub-limit for DESC was $500 million. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Long-Term and Short-Term Debt (Schedule of Line of Credit Facilities) (Detail) - Joint Revolving Credit Facility	Mar. 31, 2024 USD ($)	[1]
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	$ 1,000,000,000
Outstanding Commercial Paper	210,000,000
Outstanding Letters of Credit	$ 0

[1] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2024, the sub-limit for DESC was $500 million. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Long-Term and Short-Term Debt (Schedule of Line of Credit Facilities) (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2024 USD ($)
Minimum [Member]
Debt Instrument [Line Items]
Line of credit facility maturity date	2026-06
Maximum [Member]
Debt Instrument [Line Items]
Line of credit facility maturity date	2028-06
Joint Revolving Credit Facility
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	$ 1,000,000,000	[1]
Line of Credit Facility
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	500,000,000
Letter of Credit
Debt Instrument [Line Items]
Maximum Facility Sub-Limit	$ 1,000,000,000

[1] A maximum of $1.0 billion of the facility is available to DESC, assuming adequate capacity is available after giving effect to uses by co-borrowers Dominion Energy, Virginia Power and Questar Gas. A sub-limit for DESC is set within the facility limit but can be changed at the option of the co-borrowers multiple times per year. At March 31, 2024, the sub-limit for DESC was $500 million. If DESC has liquidity needs in excess of its sub-limit, the sub-limit may be changed or such needs may be satisfied through short-term intercompany borrowings from Dominion Energy. This credit facility matures in June 2026, with the potential to be extended by the borrowers to June 2028. The credit facility can be used to support bank borrowings and the issuance of commercial paper, as well as to support up to $1.0 billion (or the sub-limit, whichever is less) of letters of credit.

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Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Tax Disclosure [Abstract]
U.S. statutory rate	21.00%	21.00%
Increases (reductions) resulting from:
State taxes, net of federal benefit	3.90%	4.10%
Reversal of excess deferred income taxes	(5.30%)	(4.70%)
Allowance for equity funds used during construction	(0.70%)	0.00%
Settlements of uncertain tax positions	0.00%	(9.90%)
Other, net	0.00%	(0.10%)
Effective tax rate	18.90%	10.40%

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Income Taxes (Narrative) (Detail) $ in Millions	Mar. 31, 2023 USD ($)
Income Taxes [Line Items]
Income tax benefit reasonably possible to occur	$ 11

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Derivative Financial Instruments (Narrative) (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Additional collateral to its counterparties	$ 2	$ 4
Collateral already posted	0	0
Fair value of derivative instruments with credit-related contingent provisions that are in liability position and not fully collateralized with cash	$ 2	$ 4

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Derivative Financial Instruments (Offsetting Assets and Liabilities) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Assets
Derivative [Line Items]
Assets not offset in the consolidated balance sheet	[1]	$ 10	$ 0
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral received		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		10	0
Over The Counter [Member] | Assets | Interest Rate Contract [Member]
Derivative [Line Items]
Assets not offset in the consolidated balance sheet	[1]	1	0
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral received		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		1	0
Over The Counter [Member] | Assets | Commodity Contract [Member]
Derivative [Line Items]
Assets not offset in the consolidated balance sheet	[1]	9	0
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral received		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		9	0
Liability
Derivative [Line Items]
Gross liabilities presented in the consolidated balance sheet	[2]	2	4
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral paid		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		2	4
Liability | Over The Counter [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Gross liabilities presented in the consolidated balance sheet	[2]	2	4
Gross amounts not offset in the consolidated balance sheet, financial instruments		0	0
Gross amounts not offset in the consolidated balance sheet, cash collateral paid		0	0
Gross amounts not offset in the consolidated balance sheet, net amounts		$ 2	$ 4

[1] Excludes derivative assets of $245 million and $176 million at March 31, 2024 and December 31, 2023, respectively, which are not subject to master netting or similar arrangements.

[2] DESC did not have any derivative liabilities at March 31, 2024 and December 31, 2023, respectively, which were not subject to master netting or similar arrangements.

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Derivative Financial Instruments (Offsetting Assets and Liabilities) (Parenthetical) (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets not subject to master netting or similar arrangements	$ 245,000,000	$ 176,000,000
Derivative liability not subject to master netting or similar arrangements	$ 0	$ 0

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Derivative Financial Instruments (Schedule of Volume of Derivative Activity) (Detail) MWh in Millions, Bcf in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) Bcf MWh
Interest Rate Swap Current [Member]
Derivative [Line Items]
Interest rate | $	$ 0	[1]
Interest Rate Swap Current [Member] | Natural Gas (bcf)
Derivative [Line Items]
Basis | Bcf	24	[2]
Interest Rate Swap Current [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	2
Interest Rate Swap Noncurrent [Member]
Derivative [Line Items]
Interest rate | $	$ 71,000,000	[1]
Interest Rate Swap Noncurrent [Member] | Natural Gas (bcf)
Derivative [Line Items]
Basis | Bcf	0	[2]
Interest Rate Swap Noncurrent [Member] | Electricity [Member]
Derivative [Line Items]
Fixed price | MWh	23

[1] Maturity is determined based on final settlement period.

[2] Includes options.

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Derivative Financial Instruments (Fair Value of Derivatives) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Derivative Asset, Current	[1]	$ 19	$ 9
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent	[2]	$ 236	$ 167
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Assets		$ 255	$ 176
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Assets	Assets
Derivative Liability, Noncurrent	[3]	$ 2	$ 4
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Derivative Liability		$ 2	$ 4
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Liabilities and Equity	Liabilities and Equity
Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Current		$ 19	$ 9
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent		$ 235	$ 167
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Noncurrent		$ 1	$ 0
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Liability, Noncurrent		$ 2	$ 4
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Current	[1]	$ 0	$ 0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent	[2]	$ 0	$ 0
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Assets		$ 0	$ 0
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Assets	Assets
Derivative Liability, Noncurrent	[3]	$ 0	$ 0
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Derivative Liability		$ 0	$ 0
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Liabilities and Equity	Liabilities and Equity
Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Current		$ 0	$ 0
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent		$ 0	$ 0
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Noncurrent		$ 0	$ 0
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Liability, Noncurrent		$ 0	$ 0
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Current	[1]	$ 19	$ 9
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent	[2]	$ 236	$ 167
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Assets		$ 255	$ 176
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Assets	Assets
Derivative Liability, Noncurrent	[3]	$ 2	$ 4
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent
Derivative Liability		$ 2	$ 4
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Liabilities and Equity	Liabilities and Equity
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Asset, Current		$ 19	$ 9
Derivative Asset, Current, Statement of Financial Position [Extensible Enumeration]		Other Assets, Current	Other Assets, Current
Derivative Asset, Noncurrent		$ 235	$ 167
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Noncurrent		$ 1	$ 0
Derivative Asset, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Regulated Entity, Other Assets, Noncurrent	Regulated Entity, Other Assets, Noncurrent
Derivative Liability, Noncurrent		$ 2	$ 4
Derivative Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]		Liabilities, Noncurrent	Liabilities, Noncurrent

[1] Current derivative assets are presented in other current assets in DESC’s Consolidated Balance Sheets.

[2] Noncurrent derivative assets are presented in other deferred debits and other assets in DESC’s Consolidated Balance Sheets.

[3] Noncurrent derivative liabilities are presented in other deferred credits and other liabilities in DESC’s Consolidated Balance Sheets.

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Derivative Financial Instruments (Derivatives in Cash Flow Hedging Relationships) (Detail) - Cash Flow Hedging [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Derivative [Line Items]
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[1]	$ 0	$ (1)
Interest Rate Contract [Member]
Derivative [Line Items]
Increase (Decrease) in Derivatives Subject to Regulatory Treatment	[1]	$ 0	$ (1)

[1] Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/ liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Derivative Financial Instruments (Derivatives Not Designated as Hedging Instruments) (Detail) - Not Designated as Hedging Instruments [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (3)	$ 1
Commodity Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (2)	$ 1
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Utilities Operating Expense, Purchased Power	Utilities Operating Expense, Purchased Power
Interest Rate Contract [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives	[1]	$ (1)	$ 0
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Interest Expense	Interest Expense

[1] Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in the Consolidated Statements of Comprehensive Income.

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Fair Value Measurements, Including Derivatives (Schedule of Quantitative Information About Level 3 Fair Value Measurements) (Details)	Mar. 31, 2024 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 253,000,000
Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	246,000,000
Natural gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 7,000,000	[1]
Fair value inputs price volatility	34.00%	[2]
Minimum [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 24,000,000
Minimum [Member] | Natural gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 1,000,000
Fair value inputs price volatility	10.00%
Maximum [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 102,000,000
Maximum [Member] | Natural gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 3,000,000
Fair value inputs price volatility	51.00%
Weighted Average [Member] | Electricity [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 51,000,000	[2]
Weighted Average [Member] | Natural gas [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total assets, fair value	$ 2,000,000	[2]

[1] Includes basis.

[2] Averages weighted by volume.

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Fair Value Measurements, Including Derivatives (Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - Fair value, recurring - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Assets
Total assets	$ 255	$ 176
Liabilities
Total liabilities	2	4
Commodity Contract [Member]
Assets
Total assets	254	176
Interest Rate Contract [Member]
Assets
Total assets	1	0
Liabilities
Total liabilities	2	4
Level 1
Assets
Total assets	0	0
Liabilities
Total liabilities	0	0
Level 1 | Commodity Contract [Member]
Assets
Total assets	0	0
Level 1 | Interest Rate Contract [Member]
Assets
Total assets	0	0
Liabilities
Total liabilities	0	0
Level 2
Assets
Total assets	2	0
Liabilities
Total liabilities	2	4
Level 2 | Commodity Contract [Member]
Assets
Total assets	1	0
Level 2 | Interest Rate Contract [Member]
Assets
Total assets	1	0
Liabilities
Total liabilities	2	4
Level 3
Assets
Total assets	253	176
Liabilities
Total liabilities	0	0
Level 3 | Commodity Contract [Member]
Assets
Total assets	253	176
Level 3 | Interest Rate Contract [Member]
Assets
Total assets	0	0
Liabilities
Total liabilities	$ 0	$ 0

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Fair Value Measurements, Including Derivatives (Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis and Included in Level 3) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Regulatory Assets
Beginning balance	$ 176	$ 251
Included in earnings:
Purchased power	(2)	1
Settlements	2	(1)
Purchases	7
Ending balance	253	188
Other Regulatory Assets Liabilities
Included in earnings:
Included in regulatory assets/liabilities	$ 70	$ (63)

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Fair Value Measurements, Including Derivatives (Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis) (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Unrealized gains and losses	$ 0	$ 0

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Fair Value Measurements, Including Derivatives (Schedule of Carrying Values and Estimated Fair Values of Debt Instruments) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2022
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt	[1]	$ 4,219	$ 4,219
Affiliated long-term debt	[2]	230	230
Estimated Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt	[1],[3]	4,221	4,301
Affiliated long-term debt	[2],[3]	$ 230	$ 230

[1] Carrying amount includes current portions, if any, presented in securities due within one year and amounts which represent the unamortized debt issuance costs and discount or premium.

[2] Carrying amount includes current portions presented in affiliated and related party payables.

[3] Fair value is estimated using market prices, where available, and interest rates currently available for issuance of debt with similar terms and remaining maturities. All fair value measurements are classified as Level 2. The carrying amount of debt issuances with short-term maturities and variable rates refinanced at current market rates is a reasonable estimate of their fair value.

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Employee Benefit Plans (Components of Net Periodic Benefit Cost (Credit) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2	$ 2
Interest cost	8	8
Expected return on assets	(9)	(8)
Amortization of actuarial losses	2	3
Net periodic benefit cost (credit)	3	5
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0	0
Interest cost	2	2
Expected return on assets	0	0
Amortization of actuarial losses	(1)	(1)
Net periodic benefit cost (credit)	$ 1	$ 1

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Employee Benefit Plans (Narrative) (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2024	Mar. 31, 2024
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer		$ 0
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, expected contributions in 2024		$ 8
Pension Plan | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer	$ 1

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Commitments and Contingencies (Narrative) (Detail) shares in Millions		1 Months Ended														3 Months Ended		12 Months Ended
	Oct. 31, 2014 MGD Facility	Jul. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	May 31, 2022 shares	Aug. 31, 2021 shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Oct. 31, 2020	Nov. 30, 2019 gal	Jun. 30, 2018 USD ($)	Sep. 30, 2017 Petition	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Mar. 31, 2024 USD ($) Indicator Facility Product	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Loss Contingencies [Line Items]
Number of DESC facilities subject to final regulations | Facility	5
Measurement of groundwater withdrawals | gal											3,000,000
Number of manufacturing gas plant decommissioned sites that contain residues of byproduct chemicals | Product																4
Estimated environmental remediation activities at manufacturing gas plant sites																$ 5,000,000
Environmental remediation costs recognized in regulatory assets																$ 34,000,000
Number of facilities inactive subject to final rule | Facility																3
Proportionate ownership share in project												100.00%
Proposed assessment amount from SCDOR audit												$ 410,000,000
Litigation settlement expense awarded									$ 165,000,000
Real estate transfer to satisfy obligation under settlement					$ 51,000,000
Nuclear Insurance
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount																$ 16,300,000,000		$ 16,200,000,000
Maximum liability each nuclear plant is insured against																500,000,000		$ 450,000,000
Surety Bonds
Loss Contingencies [Line Items]
Guarantee obligation																$ 24,000,000
SCDOR
Loss Contingencies [Line Items]
Fair value of certain additional utility property transferred																			$ 3,000,000
Fair value of certain remaining utility property transferred			$ 11,000,000
Fair value of certain non-utility property transferred				$ 28,000,000
Fair value of certain utility property transferred																	$ 10,000,000
Gain from transferred utility property																	9,000,000
Gain from transferred utility property, after tax																	$ 7,000,000
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Litigation settlement through cash								$ 43,000,000
Shares issued on settlement | shares						0.9	0.6
Unfavorable Regulatory Action | CWA
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals with heightened entrainment analysis under CWA | MGD	2
Number of mandatory facility specific factors. | Indicator																5
Number of optional facility specific factors | Indicator																6
Personal Injury or Wrongful Death Cases
Loss Contingencies [Line Items]
Impairment of assets and other charges																$ 6,000,000
Maximum [Member] | SCDOR
Loss Contingencies [Line Items]
Cash payment		$ 1,000,000
Carbon Regulations [Member]
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T															75,000
EPA
Loss Contingencies [Line Items]
Number of petition agreed for reconsideration | Petition													2
EPA | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals under CWA | MGD	125
EPA | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Number of separate petitions for reconsideration granted | Petition														2
EPA | Minimum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies Individual circumstances period										2021
EPA | Maximum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies Individual circumstances period										2028
Environmental Protection Agency And State Regulatory Agencies
Loss Contingencies [Line Items]
Number of DESC hydroelectric facilities subject to regulations | Facility	5

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Operating Segments - Schedule of Segment Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information [Line Items]
External revenue	[1]	$ 775	$ 759
Comprehensive income (loss) available (attributable) to common shareholder		74	92
Dominion Energy South Carolina, Inc. [Member]
Segment Reporting Information [Line Items]
External revenue		775	759
Comprehensive income (loss) available (attributable) to common shareholder		75	86
Corporate and Other
Segment Reporting Information [Line Items]
External revenue		0	0
Comprehensive income (loss) available (attributable) to common shareholder		$ (1)	$ 6

[1] See Note 12 for amounts attributable to affiliates.

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
Operating Revenues - Electric from sales to affiliate		$ 1	$ 1
Operating Expenses - Other taxes from affiliate		3	3
Solar Affiliates [Member]
Related Party Transaction [Line Items]
Purchases from affiliate		1	2
Related Party | DES
Related Party Transaction [Line Items]
Direct and allocated costs	[1]	$ 53	$ 57

[1] Includes capitalized expenditures of $12 million and $16 million for the three months ended March 31, 2024 and 2023, respectively.

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Income Statement) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
DES
Related Party Transaction [Line Items]
Capitalized expenditures	$ 12	$ 16

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 133	$ 166
Derivative assets with affiliates	[1]	42	33
DES | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		41	18
SCANA Corporation | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		7	7
Public Service Company Of North Carolina Incorporated | Related Party
Related Party Transaction [Line Items]
Affiliated and related party payables and other		$ 12	$ 13

[1] Includes amounts recorded in other current assets of $2 million as of both March 31, 2024 and December 31, 2023 and amounts recorded in other deferred debits and other assets of $40 million and $31 million as of March 31, 2024 and December 31, 2023, respectively.

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Affiliated and Related Party Transactions (Schedule of Affiliated Transactions - Balance Sheet) (Parenthetical) (Detail) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Derivative assets with affiliates	[1]	$ 42	$ 33
Other Current Assets [Member]
Related Party Transaction [Line Items]
Derivative assets with affiliates		2	2
Other Deferred Debits and Other Assets [Member]
Related Party Transaction [Line Items]
Derivative assets with affiliates		$ 40	$ 31

[1] Includes amounts recorded in other current assets of $2 million as of both March 31, 2024 and December 31, 2023 and amounts recorded in other deferred debits and other assets of $40 million and $31 million as of March 31, 2024 and December 31, 2023, respectively.

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Other Income, Net (Components of Other Income, Net) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Other income		$ 2	$ 2
Gains on sales of assets	[1]	1	10
Other expense		(5)	(2)
Allowance for equity funds used during construction		3	0
Other income, net		$ 1	$ 10

[1] Includes amounts recognized in 2023 in connection with the transfer of property to satisfy litigation. See Note 10 for additional information.