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ASSET RETIREMENT OBLIGATIONS (Tables)
 12 Months Ended
Dec. 31, 2023
Asset Retirement Obligation Disclosure [Abstract]  
Details of AROs included in the balance sheets
Details of the AROs included in the balance sheets are as follows:
Southern CompanyAlabama PowerGeorgia PowerMississippi Power
Southern Power(*)
(in millions)
Balance at December 31, 2021$11,687 $4,334 $6,824 $190 $131 
Liabilities incurred36 — 35 — — 
Liabilities settled(455)(205)(212)(20)— 
Accretion expense
406 158 231 6 6 
Cash flow revisions(834)— (844)3 7 
Balance at December 31, 2022$10,840 $4,287 $6,034 $179 $144 
Liabilities incurred90 — 90 — — 
Liabilities settled(617)(270)(304)(18)— 
Accretion expense
403 156 230 5 6 
Cash flow revisions(399)(15)(385)2 — 
Balance at December 31, 2023$10,317 $4,158 $5,665 $168 $150 
(*)Included in other deferred credits and liabilities on Southern Power's consolidated balance sheets.
Investment securities in the Funds
Investment securities in the Funds for December 31, 2023 and 2022 were as follows:
Southern CompanyAlabama
Power		Georgia
Power
(in millions)
At December 31, 2023:
Equity securities$1,288 $796 $492 
Debt securities895 277 618 
Other securities239 186 53 
Total investment securities in the Funds$2,422 $1,259 $1,163 
At December 31, 2022:
Equity securities$1,095 $690 $405 
Debt securities838 267 571 
Other securities210 168 42 
Total investment securities in the Funds(*)
$2,143 $1,125 $1,018 
(*)For Southern Company and Georgia Power, these amounts include investment securities pledged to creditors and collateral received and excludes payables related to a securities lending program Georgia Power's Funds previously participated in through the managers of the Funds. Under this program, Georgia Power's Funds' investment securities were loaned to institutional investors for a fee. Securities loaned were fully collateralized by cash, letters of credit, and/or securities issued or guaranteed by the U.S. government or its agencies or instrumentalities. At December 31, 2022, approximately $35 million of the fair market value of Georgia Power's Funds' securities were on loan and pledged to creditors under the Funds' managers' securities lending program. At December 31, 2022, the fair value of the collateral received was approximately $36 million and could only be sold by the borrower upon the return of the loaned securities. The collateral received was treated as a non-cash item in the statements of cash flows.
Fair value increases (decreases) of the Funds
The fair value increases (decreases) of the Funds, including unrealized gains (losses) and reinvested interest and dividends and excluding the Funds' expenses, for 2023, 2022, and 2021 are shown in the table below.
Southern CompanyAlabama
Power		Georgia
Power
(in millions)
Fair value increases (decreases)
2023$281 $157 $124 
2022(360)(171)(189)
2021274 200 74 
Unrealized gains (losses)
At December 31, 2023$241 $119 $122 
At December 31, 2022(391)(204)(187)
At December 31, 2021(27)(30)3 
At December 31, 2023, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:
Fair Value Measurements Using
Quoted Prices in Active Markets for Identical Assets Significant Other Observable InputsSignificant Unobservable InputsNet Asset Value as a Practical Expedient
At December 31, 2023:(Level 1)(Level 2)(Level 3)(NAV)Total
(in millions)
Southern Company
Assets:
Energy-related derivatives(a)
$6 $49 $— $— $55 
Investments in trusts:(b)
Domestic equity764 216 — — 980 
Foreign equity145 171 — — 316 
U.S. Treasury and government agency securities— 369 — — 369 
Municipal bonds— 48 — — 48 
Pooled funds – fixed income— 6 — — 6 
Corporate bonds— 389 — — 389 
Mortgage and asset backed securities— 89 — — 89 
Private equity— — — 169 169 
Cash and cash equivalents3 — — — 3 
Other58 3 — 9 70 
Cash equivalents and restricted cash
253 15 — — 268 
Other investments9 27 8 — 44 
Total$1,238 $1,382 $8 $178 $2,806 
Liabilities:
Energy-related derivatives(a)
$46 $312 $— $— $358 
Interest rate derivatives— 264 — — 264 
Foreign currency derivatives— 122 — — 122 
Contingent consideration3 — 16 — 19 
Other— 13 — — 13 
Total$49 $711 $16 $— $776 
Fair Value Measurements Using
Quoted Prices in Active Markets for Identical Assets Significant Other Observable InputsSignificant Unobservable InputsNet Asset Value as a Practical Expedient
At December 31, 2023:(Level 1)(Level 2)(Level 3)(NAV)Total
(in millions)
Alabama Power
Assets:
Energy-related derivatives
$— $15 $— $— $15 
Nuclear decommissioning trusts:(b)
Domestic equity443 208 — — 651 
Foreign equity145 — — — 145 
U.S. Treasury and government agency securities— 20 — — 20 
Municipal bonds— 1 — — 1 
Corporate bonds— 231 — — 231 
Mortgage and asset backed securities— 25 — — 25 
Private equity — — — 169 169 
Other8 — — 9 17 
Cash equivalents and restricted cash
119 15 — — 134 
Other investments— 27 — — 27 
Total$715 $542 $— $178 $1,435 
Liabilities:
Energy-related derivatives$— $110 $— $— $110 
Georgia Power
Assets:
Energy-related derivatives$— $13 $— $— $13 
Nuclear decommissioning trusts:(b)
Domestic equity321 1 — — 322 
Foreign equity— 170 — — 170 
U.S. Treasury and government agency securities— 349 — — 349 
Municipal bonds— 47 — — 47 
Corporate bonds— 158 — — 158 
Mortgage and asset backed securities— 64 — — 64 
Other50 3 — — 53 
Total$371 $805 $— $— $1,176 
Liabilities:
Energy-related derivatives$— $124 $— $— $124 
Fair Value Measurements Using
Quoted Prices in Active Markets for Identical Assets Significant Other Observable InputsSignificant Unobservable InputsNet Asset Value as a Practical Expedient
At December 31, 2023:(Level 1)(Level 2)(Level 3)(NAV)Total
(in millions)
Mississippi Power
Assets:
Energy-related derivatives$— $15 $— $— $15 
Cash equivalents17 — — — 17 
Total$17 $15 $— $— $32 
Liabilities:
Energy-related derivatives$— $61 $— $— $61 
Southern Power
Assets:
Energy-related derivatives$— $3 $— $— $3 
Liabilities:
Energy-related derivatives$— $5 $— $— $5 
Foreign currency derivatives— 22 — — 22 
Contingent consideration3 — 16 — 19 
Other— 13 — — 13 
Total$3 $40 $16 $— $59 
Southern Company Gas
Assets:
Energy-related derivatives(a)
$6 $3 $— $— $9 
Non-qualified deferred compensation trusts:
Domestic equity— 7 — — 7 
Foreign equity— 1 — — 1 
Pooled funds - fixed income— 6 — — 6 
Cash and cash equivalents3 — — — 3 
Total$9 $17 $— $— $26 
Liabilities:
Energy-related derivatives(a)(b)
$46 $12 $— $— $58 
Interest rate derivatives— 79 — — 79 
Total$46 $91 $— $— $137 
(a)Excludes cash collateral of $62 million.
(b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information.
At December 31, 2022, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:
Fair Value Measurements Using
Quoted Prices in Active Markets for Identical AssetsSignificant Other Observable InputsSignificant Unobservable InputsNet Asset Value as a Practical Expedient
At December 31, 2022:(Level 1)(Level 2)(Level 3)(NAV)Total
(in millions)
Southern Company
Assets:
Energy-related derivatives(a)
$18 $181 $— $— $199 
Interest rate derivatives— 12 — — 12 
Investments in trusts:(b)(c)
Domestic equity651 178 — — 829 
Foreign equity125 150 — — 275 
U.S. Treasury and government agency securities— 285 — — 285 
Municipal bonds— 51 — — 51 
Pooled funds – fixed income— 7 — — 7 
Corporate bonds— 412 — — 412 
Mortgage and asset backed securities— 90 — — 90 
Private equity— — — 161 161 
Cash and cash equivalents4 — — — 4 
Other37 12 — — 49 
Cash equivalents1,427 20 — — 1,447 
Other investments9 26 — — 35 
Total$2,271 $1,424 $— $161 $3,856 
Liabilities:
Energy-related derivatives(a)
$32 $178 $— $— $210 
Interest rate derivatives— 302 — — 302 
Foreign currency derivatives— 216 — — 216 
Contingent consideration— — 12 — 12 
Other— 13 — — 13 
Total$32 $709 $12 $— $753 
Fair Value Measurements Using
Quoted Prices in Active Markets for Identical AssetsSignificant Other Observable InputsSignificant Unobservable InputsNet Asset Value as a Practical Expedient
At December 31, 2022:(Level 1)(Level 2)(Level 3)(NAV)Total
(in millions)
Alabama Power
Assets:
Energy-related derivatives
$— $62 $— $— $62 
Nuclear decommissioning trusts:(b)
Domestic equity396 169 — — 565 
Foreign equity125 — — — 125 
U.S. Treasury and government agency securities— 19 — — 19 
Municipal bonds— 1 — — 1 
Corporate bonds— 225 — — 225 
Mortgage and asset backed securities— 22 — — 22 
Private equity — — — 161 161 
Other7 — — — 7 
Cash equivalents438 20 — — 458 
Other investments— 26 — — 26 
Total$966 $544 $— $161 $1,671 
Liabilities:
Energy-related derivatives$— $39 $— $— $39 
Georgia Power
Assets:
Energy-related derivatives$— $42 $— $— $42 
Nuclear decommissioning trusts:(b)(c)
Domestic equity255 1 — — 256 
Foreign equity— 149 — — 149 
U.S. Treasury and government agency securities— 266 — — 266 
Municipal bonds— 50 — — 50 
Corporate bonds— 187 — — 187 
Mortgage and asset backed securities— 68 — — 68 
Other30 12 — — 42 
Cash equivalents355 — — — 355 
Total$640 $775 $— $— $1,415 
Liabilities:
Energy-related derivatives$— $62 $— $— $62 
Fair Value Measurements Using
Quoted Prices in Active Markets for Identical AssetsSignificant Other Observable InputsSignificant Unobservable InputsNet Asset Value as a Practical Expedient
At December 31, 2022:(Level 1)(Level 2)(Level 3)(NAV)Total
(in millions)
Mississippi Power
Assets:
Energy-related derivatives$— $59 $— $— $59 
Cash equivalents47 — — — 47 
Total$47 $59 $— $— $106 
Liabilities:
Energy-related derivatives$— $32 $— $— $32 
Southern Power
Assets:
Energy-related derivatives$— $8 $— $— $8 
Liabilities:
Energy-related derivatives$— $12 $— $— $12 
Foreign currency derivatives— 47 — — 47 
Contingent consideration— — 12 — 12 
Other— 13 — — 13 
Total$— $72 $12 $— $84 
Southern Company Gas
Assets:
Energy-related derivatives(a)
$18 $10 $— $— $28 
Non-qualified deferred compensation trusts:
Domestic equity— 8 — — 8 
Foreign equity— 1 — — 1 
Pooled funds - fixed income— 7 — — 7 
Cash equivalents4 — — — 4 
Cash equivalents50 — — — 50 
Total$72 $26 $— $— $98 
Liabilities:
Energy-related derivatives(a)(b)
$32 $33 $— $— $65 
Interest rate derivatives— 86 — — 86 
Total$32 $119 $— $— $151 
(a)Excludes cash collateral of $41 million.
(b)Excludes receivables related to investment income, pending investment sales, payables related to pending investment purchases, and currencies. See Note 6 under "Nuclear Decommissioning" for additional information.
(c)Includes investment securities pledged to creditors and collateral received and excludes payables related to the securities lending program. See Note 6 under "Nuclear Decommissioning" for additional information.
Accumulated provisions for the external decommissioning trust funds
At December 31, 2023 and 2022, the accumulated provisions for the external decommissioning trust funds were as follows:
20232022
(in millions)
Alabama Power
Plant Farley$1,259 $1,125 
Georgia Power
Plant Hatch$705 $628 
Plant Vogtle Units 1 and 2434 382 
Plant Vogtle Units 3 and 424 8 
Total$1,163 $1,018 
Estimated costs of decommissioning The estimated costs of decommissioning at December 31, 2023 based on the most current studies were as follows:
Alabama Power
Georgia Power
Plant
Farley
Plant
 Hatch(*)
Plant Vogtle
 Units 1 and 2(*)
Plant Vogtle
 Unit 3(*)
Most current study year
2023202120212020
Decommissioning periods:
Beginning year2037203420472063
Completion year2087207520792074
(in millions)
Site study costs:
Radiated structures$1,402 $771 $628 $284 
Spent fuel management513 186 170 30 
Non-radiated structures133 61 85 33 
Total site study costs$2,048 $1,018 $883 $347 
(*)Based on Georgia Power's ownership interests.