XML 126 R73.htm IDEA: XBRL DOCUMENT
v3.25.0.1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2024
Accounting Policies [Abstract] |
Schedule of costs for affiliate transactions | Costs for these services from SCS in 2024, 2023, and 2022 were as follows:
| Alabama Power | Georgia Power | Mississippi Power | Southern Power | Southern Company Gas
| (in millions)
2024 | $ | 813 |  | $ | 1,197 |  | $ | 130 |  | $ | 93 |  | $ | 290 |
2023 | 611 |  | 857 |  | 113 |  | 86 |  | 261 |
2022 | 549 |  | 762 |  | 115 |  | 86 |  | 262 |
Mississippi Power's and Southern Power's power purchases from affiliates through the Southern Company power pool are included in purchased power on their respective statements of income and were as follows:
| Mississippi Power | Southern Power
| (in millions)
2024 | $ | 8 |  | $ | 17 |
2023 | 4 |  | 13 |
2022 | 4 |  | 29 |
Transportation costs under these agreements in 2024, 2023, and 2022 were as follows:
| Alabama Power | Georgia Power | Southern Power | Southern Company Gas
| (in millions)
2024 | $ | 13 |  | $ | 103 |  | $ | 35 |  | $ | 28 |
2023 | 12 |  | 101 |  | 34 |  | 28 |
2022 | 18 |  | 99 |  | 37 |  | 27 |
The approximate rates for 2024, 2023, and 2022 were as follows:
| 2024 | 2023 | 2022
Alabama Power | 4.2 | % | 4.1 | % | 2.7 | %
Georgia Power | 3.4 | % | 3.8 | % | 3.3 | %
Mississippi Power | 3.3 | % | 3.4 | % | 3.4 | %
Southern Company Gas | 2.9 | % | 2.7 | % | 2.7 | %
Schedule of total AFUDC and interest capitalized | Total AFUDC and interest capitalized for the applicable Registrants in 2024, 2023, and 2022 was as follows:
| Southern Company | Alabama Power | Georgia Power(*) |  | Southern Power | Southern Company Gas
| (in millions)
2024 | $ | 339 |  | $ | 76 |  | $ | 209 |  |  | $ | 7 |  | $ | 47 |
2023 | 400 |  | 109 |  | 251 |  |  | 3 |  | 37 |
2022 | 327 |  | 90 |  | 213 |  |  | — |  | 24 |
(*)See Note 2 under "Georgia Power – Nuclear Construction" for information on the inclusion of a portion of construction costs related to Plant Vogtle Units 3 and 4 in Georgia Power's rate base through each unit's respective in-service date.
Schedule of average AFUDC composite rates | The average AFUDC composite rates for 2024, 2023, and 2022 for the traditional electric operating companies and the natural gas distribution utilities were as follows:
| 2024 | 2023 | 2022
Alabama Power | 8.1 | % | 8.1 | % | 7.9 | %
Georgia Power(a) | 7.7 | % | 7.6 | % | 7.3 | %
Mississippi Power(b) | — | % | — | % | 5.3 | %
Southern Company Gas: |  |  |
Atlanta Gas Light | 7.7 | % | 7.4 | % | 7.6 | %
Chattanooga Gas | 7.1 | % | 7.1 | % | 7.1 | %
Nicor Gas | 5.6 | % | 4.6 | % | 2.0 | %
(a)Excludes AFUDC related to the construction of Plant Vogtle Units 3 and 4 in 2022 and 2023 and Plant Vogtle Unit 4 in 2024. See Note 2 under "Georgia Power – Nuclear Construction" for additional information. (b)Mississippi Power's AFUDC was immaterial in 2024 and 2023.
Schedule of goodwill balances | At December 31, 2024 and 2023, goodwill was as follows:
| At December 31, 2024 | At December 31, 2023
| (in millions)
Southern Company | $ | 5,161 |  | $ | 5,161 |
Southern Company Gas: |  |
Gas distribution operations | $ | 4,034 |  | $ | 4,034 |
Gas marketing services | 981 |  | 981 |
Southern Company Gas total | $ | 5,015 |  | $ | 5,015 |
Schedule of intangible assets subject to amortization | At December 31, 2024 and 2023, other intangible assets were as follows:
| At December 31, 2024 |  | At December 31, 2023
| Gross Carrying Amount | Accumulated Amortization | Other Intangible Assets, Net |  | Gross Carrying Amount | Accumulated Amortization | Other Intangible Assets, Net
| (in millions) |  | (in millions)
Southern Company |  |  |  |  |  |  |
Subject to amortization: |  |  |  |  |  |  |
Customer relationships | $ | 212 |  | $ | (182) |  | $ | 30 |  |  | $ | 212 |  | $ | (172) |  | $ | 40 |
Trade names | 64 |  | (59) |  | 5 |  |  | 64 |  | (53) |  | 11 |
PPA fair value adjustments | 390 |  | (168) |  | 222 |  |  | 390 |  | (148) |  | 242 |
Other | 3 |  | (3) |  | — |  |  | 3 |  | (3) |  | — |
Total subject to amortization | $ | 669 |  | $ | (412) |  | $ | 257 |  |  | $ | 669 |  | $ | (376) |  | $ | 293 |
Not subject to amortization: |  |  |  |  |  |  |
FCC licenses | 75 |  | — |  | 75 |  |  | 75 |  | — |  | 75 |
Total other intangible assets | $ | 744 |  | $ | (412) |  | $ | 332 |  |  | $ | 744 |  | $ | (376) |  | $ | 368 |
Southern Power(*) |  |  |  |  |  |  |
PPA fair value adjustments | $ | 390 |  | $ | (168) |  | $ | 222 |  |  | $ | 390 |  | $ | (148) |  | $ | 242 |
Southern Company Gas(*) |  |  |  |  |  |  |
Gas marketing services |  |  |  |  |  |  |
Customer relationships | $ | 156 |  | $ | (150) |  | $ | 6 |  |  | $ | 156 |  | $ | (145) |  | $ | 11 |
Trade names | 26 |  | (23) |  | 3 |  |  | 26 |  | (21) |  | 5 |
Total other intangible assets | $ | 182 |  | $ | (173) |  | $ | 9 |  |  | $ | 182 |  | $ | (166) |  | $ | 16 |
(*)All subject to amortization.
Schedule of intangible assets not subject to amortization | At December 31, 2024 and 2023, other intangible assets were as follows:
| At December 31, 2024 |  | At December 31, 2023
| Gross Carrying Amount | Accumulated Amortization | Other Intangible Assets, Net |  | Gross Carrying Amount | Accumulated Amortization | Other Intangible Assets, Net
| (in millions) |  | (in millions)
Southern Company |  |  |  |  |  |  |
Subject to amortization: |  |  |  |  |  |  |
Customer relationships | $ | 212 |  | $ | (182) |  | $ | 30 |  |  | $ | 212 |  | $ | (172) |  | $ | 40 |
Trade names | 64 |  | (59) |  | 5 |  |  | 64 |  | (53) |  | 11 |
PPA fair value adjustments | 390 |  | (168) |  | 222 |  |  | 390 |  | (148) |  | 242 |
Other | 3 |  | (3) |  | — |  |  | 3 |  | (3) |  | — |
Total subject to amortization | $ | 669 |  | $ | (412) |  | $ | 257 |  |  | $ | 669 |  | $ | (376) |  | $ | 293 |
Not subject to amortization: |  |  |  |  |  |  |
FCC licenses | 75 |  | — |  | 75 |  |  | 75 |  | — |  | 75 |
Total other intangible assets | $ | 744 |  | $ | (412) |  | $ | 332 |  |  | $ | 744 |  | $ | (376) |  | $ | 368 |
Southern Power(*) |  |  |  |  |  |  |
PPA fair value adjustments | $ | 390 |  | $ | (168) |  | $ | 222 |  |  | $ | 390 |  | $ | (148) |  | $ | 242 |
Southern Company Gas(*) |  |  |  |  |  |  |
Gas marketing services |  |  |  |  |  |  |
Customer relationships | $ | 156 |  | $ | (150) |  | $ | 6 |  |  | $ | 156 |  | $ | (145) |  | $ | 11 |
Trade names | 26 |  | (23) |  | 3 |  |  | 26 |  | (21) |  | 5 |
Total other intangible assets | $ | 182 |  | $ | (173) |  | $ | 9 |  |  | $ | 182 |  | $ | (166) |  | $ | 16 |
(*)All subject to amortization.
Schedule of amortization associated with other intangible assets | Amortization associated with other intangible assets in 2024, 2023, and 2022 was as follows:
| 2024 | 2023 | 2022
| (in millions)
Southern Company(a) | $ | 35 |  | $ | 38 |  | $ | 39 |
Southern Power(b) | 20 |  | 20 |  | 20 |
Southern Company Gas |  |  |
Gas marketing services | 7 |  | 10 |  | 11 |
(a)Includes $20 million annually recorded as a reduction to operating revenues. (b)Recorded as a reduction to operating revenues.
Schedule of estimated future amortization of other intangible assets | At December 31, 2024, the estimated amortization associated with other intangible assets for the next five years is as follows:
| 2025 | 2026 | 2027 | 2028 | 2029
| (in millions)
Southern Company | $ | 32 |  | $ | 27 |  | $ | 23 |  | $ | 23 |  | $ | 23 |
Southern Power | 20 |  | 20 |  | 20 |  | 20 |  | 19 |
Southern Company Gas |  |  |  |  |
Gas marketing services | 6 |  | 3 |  | — |  | — |  | — |
Schedule of cash, cash equivalents, and restricted cash | The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that total to the amount shown in the statements of cash flows for the applicable Registrants:
| Southern Company | Alabama Power | Georgia Power | Southern Power | Southern Company Gas
| (in millions)
At December 31, 2024 |  |  |  |  |
Cash and cash equivalents | $ | 1,070 |  | $ | 585 |  | $ | 97 |  | $ | 159 |  | $ | 43 |
Restricted cash(a): |  |  |  |  |
Other current assets | 31 |  | — |  | 21 |  | 9 |  | 1 |
Total cash, cash equivalents, and restricted cash(b) | $ | 1,101 |  | $ | 585 |  | $ | 118 |  | $ | 168 |  | $ | 44 |
At December 31, 2023 |  |  |  |  |
Cash and cash equivalents | $ | 748 |  | $ | 324 |  | $ | 9 |  | $ | 124 |  | $ | 33 |
Restricted cash(a): |  |  |  |  |
Other current assets | 141 |  | 85 |  | 37 |  | 17 |  | 2 |
Other deferred charges and assets | 31 |  | — |  | 29 |  | 3 |  | — |
Total cash, cash equivalents, and restricted cash(b) | $ | 921 |  | $ | 409 |  | $ | 75 |  | $ | 144 |  | $ | 35 |
(a)For Alabama Power and Georgia Power, reflects proceeds from the issuance of solid waste disposal facility revenue bonds in 2023 and 2022, respectively. See Note 8 under "Long-term Debt" for additional information. For Southern Power, reflects $9 million and $17 million at December 31, 2024 and 2023, respectively, resulting from an arbitration award held to fund future replacement costs and $3 million at December 31, 2023 held to fund estimated construction completion costs at the Deuel Harvest wind facility. For Southern Company Gas, reflects collateral for workers' compensation, life insurance, and long-term disability insurance. (b)Total may not add due to rounding.
Reconciliation of restricted cash and cash equivalents | The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that total to the amount shown in the statements of cash flows for the applicable Registrants:
| Southern Company | Alabama Power | Georgia Power | Southern Power | Southern Company Gas
| (in millions)
At December 31, 2024 |  |  |  |  |
Cash and cash equivalents | $ | 1,070 |  | $ | 585 |  | $ | 97 |  | $ | 159 |  | $ | 43 |
Restricted cash(a): |  |  |  |  |
Other current assets | 31 |  | — |  | 21 |  | 9 |  | 1 |
Total cash, cash equivalents, and restricted cash(b) | $ | 1,101 |  | $ | 585 |  | $ | 118 |  | $ | 168 |  | $ | 44 |
At December 31, 2023 |  |  |  |  |
Cash and cash equivalents | $ | 748 |  | $ | 324 |  | $ | 9 |  | $ | 124 |  | $ | 33 |
Restricted cash(a): |  |  |  |  |
Other current assets | 141 |  | 85 |  | 37 |  | 17 |  | 2 |
Other deferred charges and assets | 31 |  | — |  | 29 |  | 3 |  | — |
Total cash, cash equivalents, and restricted cash(b) | $ | 921 |  | $ | 409 |  | $ | 75 |  | $ | 144 |  | $ | 35 |
(a)For Alabama Power and Georgia Power, reflects proceeds from the issuance of solid waste disposal facility revenue bonds in 2023 and 2022, respectively. See Note 8 under "Long-term Debt" for additional information. For Southern Power, reflects $9 million and $17 million at December 31, 2024 and 2023, respectively, resulting from an arbitration award held to fund future replacement costs and $3 million at December 31, 2023 held to fund estimated construction completion costs at the Deuel Harvest wind facility. For Southern Company Gas, reflects collateral for workers' compensation, life insurance, and long-term disability insurance. (b)Total may not add due to rounding.
Schedule of regulatory assets | Storm damage reserve activity for the traditional electric operating companies during 2023 and 2024 was as follows:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power
| (in millions)
Balance at December 31, 2022 | $ | 216 |  | $ | 97 |  | $ | 83 |  | $ | 36 |
Accrual | 61 |  | 18 |  | 31 |  | 12 |
Weather-related damages | (211) |  | (39) |  | (168) |  | (4) |
Balance at December 31, 2023 | $ | 66 |  | $ | 76 |  | $ | (54) |  | $ | 44 |
Accrual | 79 |  | 34 |  | 31 |  | 14 |
Weather-related damages | (850) |  | (40) |  | (804) |  | (6) |
Balance at December 31, 2024 | $ | (705) |  | $ | 70 |  | $ | (827) |  | $ | 52 |
The traditional electric operating companies accrued the following amounts related to storm damage recovery in 2022:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power
| (in millions)
2022 | $ | 239 |  | $ | 19 |  | $ | 213 |  | $ | 7 |
During 2024, 2023, and 2022, Alabama Power and Mississippi Power accrued the following amounts to their reliability reserves:
| Southern Company | Alabama Power | Mississippi Power
| (in millions)
2024 | $ | 84 |  | $ | 63 |  | $ | 21 |
2023 | 63 |  | 52 |  | 11 |
2022 | 191 |  | 166 |  | 25 |
Details of regulatory assets and (liabilities) reflected in the balance sheets at December 31, 2024 and 2023 are provided in the following tables:
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Company Gas
| (in millions)
At December 31, 2024 |  |  |  |  |
AROs(*) | $ | 5,810 |  | $ | 1,906 |  | $ | 3,658 |  | $ | 248 |  | $ | — |
Retiree benefit plans(*) | 2,605 |  | 680 |  | 892 |  | 134 |  | 44 |
Remaining net book value of retired assets | 1,198 |  | 454 |  | 729 |  | 15 |  | — |
Deferred income tax charges | 927 |  | 264 |  | 634 |  | 27 |  | — |
Storm damage | 859 |  | — |  | 827 |  | 32 |  | — |
Deferred depreciation | 535 |  | 286 |  | 249 |  | — |  | — |
Environmental remediation(*) | 249 |  | — |  | 16 |  | — |  | 233 |
Vacation pay(*) | 224 |  | 85 |  | 112 |  | 12 |  | 15 |
Loss on reacquired debt | 219 |  | 32 |  | 183 |  | 4 |  | — |
Software and cloud computing costs | 200 |  | 76 |  | 116 |  | 4 |  | 4 |
Under recovered regulatory clause revenues | 167 |  | 119 |  | — |  | 17 |  | 31 |
Regulatory clauses | 162 |  | 82 |  | — |  | — |  | 80 |
Nuclear outage | 92 |  | 39 |  | 53 |  | — |  | — |
Fuel-hedging (realized and unrealized) losses | 69 |  | 23 |  | 29 |  | 17 |  | — |
Qualifying repairs of natural gas distribution systems | 53 |  | — |  | — |  | — |  | 53 |
Long-term debt fair value adjustment | 52 |  | — |  | — |  | — |  | 52 |
Plant Daniel Units 3 and 4 | 23 |  | — |  | — |  | 23 |  | — |
Other regulatory assets | 184 |  | 42 |  | 40 |  | 30 |  | 72 |
Deferred income tax credits | (4,536) |  | (1,398) |  | (2,149) |  | (219) |  | (755) |
Other cost of removal obligations | (1,176) |  | 24 |  | 816 |  | (170) |  | (1,846) |
Over recovered regulatory clause revenues | (285) |  | (29) |  | (52) |  | — |  | (204) |
Reliability reserves | (188) |  | (131) |  | — |  | (57) |  | — |
Storm/property damage reserves | (122) |  | (70) |  | — |  | (52) |  | — |
Nuclear fuel disposal cost recovery | (100) |  | (100) |  | — |  | — |  | — |
Other regulatory liabilities | (180) |  | (28) |  | (14) |  | (6) |  | (31) |
Total regulatory assets (liabilities), net | $ | 7,041 |  | $ | 2,356 |  | $ | 6,139 |  | $ | 59 |  | $ | (2,252) |
| Southern Company | Alabama Power | Georgia Power | Mississippi Power | Southern Company Gas
| (in millions)
At December 31, 2023 |  |  |  |  |
AROs(*) | $ | 5,733 |  | $ | 1,936 |  | $ | 3,505 |  | $ | 247 |  | $ | — |
Retiree benefit plans(*) | 3,011 |  | 815 |  | 976 |  | 140 |  | 146 |
Remaining net book value of retired assets | 1,357 |  | 499 |  | 841 |  | 17 |  | — |
Deferred income tax charges | 897 |  | 262 |  | 605 |  | 28 |  | — |
Under recovered regulatory clause revenues | 413 |  | 381 |  | — |  | 12 |  | 20 |
Fuel-hedging (realized and unrealized) losses | 270 |  | 100 |  | 121 |  | 49 |  | — |
Deferred depreciation | 270 |  | 143 |  | 127 |  | — |  | — |
Environmental remediation(*) | 255 |  | — |  | 20 |  | — |  | 235 |
Loss on reacquired debt | 238 |  | 35 |  | 197 |  | 5 |  | 1 |
Vacation pay(*) | 217 |  | 83 |  | 107 |  | 11 |  | 16 |
Software and cloud computing costs | 150 |  | 59 |  | 84 |  | 2 |  | 5 |
Regulatory clauses | 140 |  | 112 |  | — |  | — |  | 28 |
Storm damage | 92 |  | — |  | 54 |  | 38 |  | — |
Nuclear outage | 83 |  | 50 |  | 33 |  | — |  | — |
Long-term debt fair value adjustment | 60 |  | — |  | — |  | — |  | 60 |
Qualifying repairs of natural gas distribution systems | 40 |  | — |  | — |  | — |  | 40 |
Plant Daniel Units 3 and 4 | 25 |  | — |  | — |  | 25 |  | — |
Other regulatory assets | 189 |  | 39 |  | 33 |  | 25 |  | 93 |
Deferred income tax credits | (4,686) |  | (1,506) |  | (2,161) |  | (241) |  | (759) |
Other cost of removal obligations | (1,312) |  | 28 |  | 617 |  | (186) |  | (1,771) |
Over recovered regulatory clause revenues | (287) |  | (3) |  | (46) |  | — |  | (238) |
Reliability reserves | (179) |  | (143) |  | — |  | (36) |  | — |
Storm/property damage reserves | (120) |  | (76) |  | — |  | (44) |  | — |
Other regulatory liabilities | (333) |  | (94) |  | (23) |  | (2) |  | (101) |
Total regulatory assets (liabilities), net | $ | 6,523 |  | $ | 2,720 |  | $ | 5,090 |  | $ | 90 |  | $ | (2,225) |
(*)Generally not earning a return as they are excluded from rate base or are offset in rate base by a corresponding asset or liability. Unless otherwise noted, the following recovery and amortization periods for these regulatory assets and (liabilities) have been approved by the respective state PSC or regulatory agency: AROs and other cost of removal obligations – Generally recorded over the related property lives, which may range up to 64 years for Alabama Power, 54 years for Georgia Power, 67 years for Mississippi Power, and 85 years for Southern Company Gas. AROs and other cost of removal obligations are settled and trued up following completion of the related activities. Alabama Power is recovering CCR ARO expenditures over a 38-year period ending in 2054 through Rate CNP Compliance. Effective January 1, 2023, Georgia Power is recovering CCR ARO expenditures over four-year periods through its ECCR tariff. Prior to 2023, expenditures were recovered over three-year periods. See "Georgia Power – Rate Plans" herein and Note 6 for additional information. Retiree benefit plans – Recovered and amortized over the average remaining service period, which may range up to 14 years for Alabama Power, Georgia Power, Mississippi Power, and Southern Company Gas. Southern Company's balances also include amounts at SCS and Southern Nuclear that are allocated to the applicable regulated utilities. See Note 11 for additional information. Remaining net book value of retired assets – Alabama Power: Primarily represents the net book value of Plant Gorgas Unit 10 ($419 million at December 31, 2024) being amortized over 13 years (through 2037) and Plant Barry Unit 4 ($35 million at December 31, 2024) being amortized over 10 years (through 2034). See "Alabama Power – Environmental Accounting Order" herein for additional information. Georgia Power: Net book values of Plant Wansley Units 1 and 2 and Plant Hammond Units 3 and 4 (totaling $418 million and $302 million, respectively, at December 31, 2024) are being amortized over remaining periods between one and 11 years (between 2025 and 2035). Balance also includes unusable materials and supplies inventories, for which the Georgia PSC will determine a recovery period in a future base rate case. Mississippi Power: Represents net book value of certain environmental compliance assets at Plant Watson and Plant Greene County. The retail portion is being amortized over 10 years (through 2033) and the wholesale portion is being amortized over 10 years (through 2034). See "Mississippi Power – Environmental Compliance Overview Plan" herein for additional information. Deferred income tax charges and credits – Charges are recovered and credits are primarily amortized over the related property lives, which may range up to 64 years for Alabama Power, 54 years for Georgia Power, 67 years for Mississippi Power, and 85 years for Southern Company Gas. See Note 10 for additional information. These accounts include certain deferred income tax assets and liabilities not subject to normalization, as described further below: Alabama Power: Related amounts at December 31, 2024 include excess federal deferred income tax liabilities that are available for the benefit of customers in 2025, as discussed under "Alabama Power – Excess Accumulated Deferred Income Tax Accounting Order" herein. Remaining amounts are being recovered and amortized ratably over the related property lives. Georgia Power: Related amounts at December 31, 2024 include $135 million of deferred income tax assets related to construction costs for Plant Vogtle Units 3 and 4 being recovered over 10 years (through 2034) and $102 million of excess state deferred income tax liabilities that will be returned to customers in 2025. See "Georgia Power – Nuclear Construction – Regulatory Matters" herein for additional information on recovery of costs related to Plant Vogtle Units 3 and 4. Southern Company Gas: Related amounts at December 31, 2024 include $24 million of deferred income tax liabilities being amortized over periods generally not exceeding five years, primarily related to excess state deferred income tax liabilities. See "Southern Company Gas – Rate Proceedings" herein for additional information. Storm damage – See "Georgia Power – Storm Damage Recovery" herein and Note 1 under "Storm Damage and Reliability Reserves" for additional information. Mississippi Power's balance represents deferred storm costs associated with Hurricanes Ida and Zeta being recovered through PEP over seven years (through 2029). Deferred depreciation – Alabama Power: Represents deferred depreciation for Plant Barry Unit 5 ($114 million at December 31, 2024) and Plant Barry common coal assets ($48 million at December 31, 2024) to be amortized until 2036 beginning when Plant Barry Unit 5 is retired and Plant Gaston Unit 5 coal assets ($124 million at December 31, 2024) to be amortized until 2039 beginning when the assets are retired. Georgia Power: Represents deferred depreciation for Plant Scherer Units 1 through 3 ($139 million at December 31, 2024) to be amortized over six years beginning in 2029 and Plant Bowen Units 1 and 2 ($80 million at December 31, 2024) to be amortized over four years beginning in 2031, both as approved under Georgia Power's 2022 ARP, and Plant Vogtle Unit 3 and common facilities ($29 million at December 31, 2024) being amortized over 10 years (through 2034). See "Georgia Power – Nuclear Construction – Regulatory Matters" herein for additional information on recovery of costs related to Plant Vogtle Units 3 and 4. Environmental remediation – Effective January 1, 2023, Georgia Power is recovering $5 million annually for environmental remediation under the 2022 ARP. Southern Company Gas' costs are recovered through environmental cost recovery mechanisms when the remediation work is performed. See Note 3 under "Environmental Remediation" for additional information. Vacation pay – Recorded as earned by employees and recovered as paid, generally within one year. Includes both vacation and banked holiday pay, if applicable. Loss on reacquired debt – Recovered over either the remaining life of the original issue or, if refinanced, over the remaining life of the new issue. At December 31, 2024, the remaining amortization periods do not exceed 23 years for Alabama Power, 28 years for Georgia Power, 17 years for Mississippi Power, and three years for Southern Company Gas. Software and cloud computing costs – Represents certain deferred operations and maintenance costs associated with software and cloud computing projects. For Alabama Power, costs are amortized ratably over the life of the related software, which ranges up to 10 years (through 2034). For Georgia Power, costs incurred through 2022 are being amortized over five years (through 2027), and the recovery period for costs incurred after 2022 will be determined in its next base rate case. For Mississippi Power, the recovery period will be determined in Mississippi Power's annual PEP filing process following the completion of the projects and is expected to begin no earlier than 2026. For Southern Company Gas, costs are being amortized ratably over the life of the related software, which ranges up to 10 years (through 2034). Under and over recovered regulatory clause revenues – Alabama Power: Balances are recorded monthly and expected to be recovered over periods of up to six years, with the majority expected to be recovered within one year. See "Alabama Power – Rate CNP PPA," " – Rate CNP Compliance," and " – Rate ECR" herein for additional information. Georgia Power: Balances are recorded monthly and expected to be recovered or returned within two years. See "Georgia Power – Rate Plans" herein for additional information. Mississippi Power: At December 31, 2024, $17 million is expected to be recovered through various rate recovery mechanisms over a period to be determined in future rate filings. See "Mississippi Power – Ad Valorem Tax Adjustment" herein for additional information. Southern Company Gas: Balances are recorded and recovered or amortized over periods generally not exceeding five years. In addition to natural gas cost recovery mechanisms, the natural gas distribution utilities have various other cost recovery mechanisms for the recovery of costs, including those related to infrastructure replacement programs. Regulatory clauses – Alabama Power: Effective January 1, 2023, balance is being amortized through Rate RSE over a five-year period ending in 2027. Southern Company Gas: Represents amounts related to Nicor Gas' volume balancing adjustment rider expected to be recovered over a period of less than two years. Nuclear outage – Costs are deferred to a regulatory asset when incurred and amortized over a subsequent period of 18 months for Alabama Power and up to 24 months for Georgia Power. See Note 5 for additional information. Fuel-hedging (realized and unrealized) losses and gains – Assets and liabilities are recorded over the life of the underlying hedged purchase contracts. Upon final settlement, actual costs incurred are recovered through the applicable traditional electric operating company's fuel cost recovery mechanism. Purchase contracts generally do not exceed three and a half years for Alabama Power, three years for Georgia Power, and four years for Mississippi Power. Immaterial amounts for fuel-hedging gains at December 31, 2024 and 2023 are included in other regulatory liabilities. Qualifying repairs of natural gas distribution systems – Represents deferred costs of certain repairs at Atlanta Gas Light being amortized over 20 years. Long-term debt fair value adjustment – Recovered over the remaining lives of the original debt issuances at acquisition, which range up to 14 years at December 31, 2024. Plant Daniel Units 3 and 4 – Represents the difference between Mississippi Power's revenue requirement for Plant Daniel Units 3 and 4 under purchase accounting and operating lease accounting. At December 31, 2024, consists of the $16 million retail portion being amortized through 2039 over the remaining life of the related property and the $8 million wholesale portion being amortized over 10 years (through 2034). Other regulatory assets – Comprised of numerous immaterial components with remaining amortization periods at December 31, 2024 generally not exceeding 19 years for Alabama Power, 10 years for Georgia Power, 10 years for Mississippi Power, and 15 years for Southern Company Gas. Reliability reserves and storm/property damage reserves – Utilized as related expenses are incurred. See "Alabama Power – Rate NDR" and " – Reliability Reserve Accounting Order," "Georgia Power – Storm Damage Recovery," and "Mississippi Power – System Restoration Rider" and " – Reliability Reserve Accounting Order" herein and Note 1 under "Storm Damage and Reliability Reserves" for additional information. Nuclear fuel disposal cost recovery – Represents award resulting from litigation related to nuclear fuel disposal costs. See Note 3 under "Nuclear Fuel Disposal Costs" for additional information. Other regulatory liabilities – Comprised of numerous immaterial components with remaining amortization periods at December 31, 2024 generally not exceeding one year for Alabama Power, three years for Georgia Power, one year for Mississippi Power, and 20 years for Southern Company Gas. The following table illustrates Southern Company Gas' authorized ratemaking amounts that are not recognized on its balance sheets. These amounts are primarily comprised of an allowed equity rate of return on assets associated with certain regulatory infrastructure programs. These amounts will be recognized as revenues in Southern Company Gas' financial statements in the periods they are billable to customers, the majority of which will be recovered by 2025.
| December 31, 2024 |  | December 31, 2023
| (in millions)
Atlanta Gas Light | $ | 11 |  |  | $ | 23 |
Virginia Natural Gas | 10 |  |  | 10 |
Chattanooga Gas | 7 |  |  | 7 |
Nicor Gas | — |  |  | 3 |
Total | $ | 28 |  |  | $ | 43 |
Schedule of AOCI (loss) balances, net of tax effects | AOCI (loss) balances, net of tax effects, for Southern Company, Southern Power, and Southern Company Gas were as follows:
| Qualifying Hedges |  | Pension and Other Postretirement Benefit Plans |  | Accumulated Other Comprehensive Income (Loss)(*)
| (in millions)
Southern Company |  |  |  |  |
Balance at December 31, 2021 | $ | (162) |  |  | $ | (76) |  |  | $ | (237) |
Current period change | 13 |  |  | 58 |  |  | 71 |
Balance at December 31, 2022 | (149) |  |  | (18) |  |  | (167) |
Current period change | 28 |  |  | (38) |  |  | (10) |
Balance at December 31, 2023 | (121) |  |  | (56) |  |  | (177) |
Current period change | 75 |  |  | 24 |  |  | 99 |
Balance at December 31, 2024 | $ | (46) |  |  | $ | (32) |  |  | $ | (78) |
Southern Power |  |  |  |  |
Balance at December 31, 2021 | $ | 1 |  |  | $ | (29) |  |  | $ | (27) |
Current period change | (10) |  |  | 20 |  |  | 10 |
Balance at December 31, 2022 | (9) |  |  | (9) |  |  | (18) |
Current period change | 8 |  |  | (7) |  |  | 1 |
Balance at December 31, 2023 | (1) |  |  | (16) |  |  | (17) |
Current period change | 8 |  |  | 7 |  |  | 15 |
Balance at December 31, 2024 | $ | 7 |  |  | $ | (9) |  |  | $ | (2) |
Southern Company Gas |  |  |  |  |
Balance at December 31, 2021 | $ | (14) |  |  | $ | 38 |  |  | $ | 24 |
Current period change | (11) |  |  | 18 |  |  | 7 |
Balance at December 31, 2022 | (25) |  |  | 56 |  |  | 31 |
Current period change | 1 |  |  | (16) |  |  | (15) |
Balance at December 31, 2023 | (24) |  |  | 40 |  |  | 16 |
Current period change | 21 |  |  | 11 |  |  | 32 |
Balance at December 31, 2024 | $ | (3) |  |  | $ | 51 |  |  | $ | 48 |
(*)May not add due to rounding.

X
- Definition Allowance For Funds Used During Construction And Interest Capitalized, Composite Rates [Table Text Block] + References No definition available. + Details
Name: | so_AllowanceForFundsUsedDuringConstructionAndInterestCapitalizedCompositeRatesTableTextBlock
Namespace Prefix: | so_
Data Type: | dtr-types1:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Allowance For Funds Used During Construction And Interest Capitalized [Table Text Block] + References No definition available. + Details
Name: | so_AllowanceForFundsUsedDuringConstructionAndInterestCapitalizedTableTextBlock
Namespace Prefix: | so_
Data Type: | dtr-types1:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of amortization expense of assets, excluding financial assets, that lack physical substance, having a limited useful life. + References No definition available. + Details
Name: | us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of accumulated other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-14A Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481674/830-30-50-1 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 830 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147481694/830-30-45-20 + Details
Name: | us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the components of cash and cash equivalents. + References No definition available. + Details
Name: | us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of assets, excluding financial assets and goodwill, lacking physical substance with a finite life, by either major class or business segment. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 40 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482640/350-30-55-40 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of goodwill by reportable segment and in total which includes a rollforward schedule. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 24 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482548/350-20-55-24 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1 Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1A -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-1A Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482573/350-20-50-2 + Details
Name: | us-gaap_ScheduleOfGoodwillTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of assets, excluding financial assets and goodwill, lacking physical substance and exist in perpetuity, by either major class or business segment. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 40 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482640/350-30-55-40 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 715 -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478574/980-715-50-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-2 + Details
Name: | us-gaap_ScheduleOfRegulatoryAssetsTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of related party transactions. Examples of related party transactions include, but are not limited to, transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners and (d) affiliates. + References No definition available. + Details
Name: | us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of cash and cash equivalents restricted as to withdrawal or usage. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(1)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 8 -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482913/230-10-50-8 + Details
Name: | us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the amount of amortization expense expected to be recorded in succeeding fiscal years for finite-lived intangible assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 55 -Paragraph 40 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482640/350-30-55-40 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 350 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(3) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482665/350-30-50-2 + Details
Name: | us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration