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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.