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Retirement Benefits | 9 Months Ended
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Sep. 30, 2025
Retirement Benefits [Abstract] |
Retirement Benefits | RETIREMENT BENEFITS The Southern Company system has a qualified defined benefit, trusteed, pension plan covering substantially all employees, with the exception of employees at PowerSecure. The qualified pension plan is funded in accordance with requirements of the Employee Retirement Income Security Act of 1974, as amended. No mandatory contributions to the qualified pension plan are anticipated for the year ending December 31, 2025. The Southern Company system also provides certain non-qualified defined benefits for a select group of management and highly compensated employees, which are funded on a cash basis. In addition, the Southern Company system provides certain medical care and life insurance benefits for retired employees through other postretirement benefit plans. The traditional electric operating companies fund other postretirement trusts to the extent required by their respective regulatory commissions. See Note 11 to the financial statements in Item 8 of the Form 10-K for additional information. On each Registrant's condensed statements of income, the service cost component of net periodic benefit costs is included in other operations and maintenance expenses and all other components of net periodic benefit costs are included in other income (expense), net. Components of the net periodic benefit costs for the three and nine months ended September 30, 2025 and 2024 are presented in the following tables.
| Southern Company |  | Alabama Power |  | Georgia Power |  | Mississippi Power |  | Southern Power |  | Southern Company Gas
| (in millions)
Three Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |  |
Pension Plans |  |  |  |  |  |  |  |  |  |  |
Service cost | $ | 66 |  |  | $ | 15 |  |  | $ | 16 |  |  | $ | 3 |  |  | $ | 1 |  |  | $ | 7 |
Interest cost | 166 |  |  | 39 |  |  | 49 |  |  | 7 |  |  | 2 |  |  | 11 |
Expected return on plan assets | (320) |  |  | (78) |  |  | (100) |  |  | (15) |  |  | (4) |  |  | (22) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (1) |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 4 |
Net loss | 9 |  |  | 2 |  |  | 5 |  |  | 2 |  |  | 1 |  |  | — |
Net periodic pension income | $ | (79) |  |  | $ | (22) |  |  | $ | (30) |  |  | $ | (3) |  |  | $ | — |  |  | $ | (1) |
Postretirement Benefits |  |  |  |  |  |  |  |  |  |  |
Service cost | $ | 4 |  |  | $ | 1 |  |  | $ | 1 |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Interest cost | 17 |  |  | 5 |  |  | 6 |  |  | 1 |  |  | — |  |  | 2 |
Expected return on plan assets | (23) |  |  | (8) |  |  | (9) |  |  | (1) |  |  | — |  |  | (2) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | 1 |  |  | — |  |  | 1 |  |  | — |  |  | — |  |  | — |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 1 |
Net gain | (4) |  |  | (2) |  |  | — |  |  | — |  |  | — |  |  | (2) |
Net periodic postretirement benefit income | $ | (5) |  |  | $ | (4) |  |  | $ | (1) |  |  | $ | — |  |  | $ | — |  |  | $ | (1) |
Nine Months Ended September 30, 2025 |  |  |  |  |  |  |  |  |  |
Pension Plans
Service cost | $ | 198 |  |  | $ | 45 |  |  | $ | 47 |  |  | $ | 8 |  |  | $ | 4 |  |  | $ | 20 |
Interest cost | 498 |  |  | 116 |  |  | 147 |  |  | 22 |  |  | 7 |  |  | 33 |
Expected return on plan assets | (960) |  |  | (234) |  |  | (298) |  |  | (44) |  |  | (12) |  |  | (65) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | — |  |  | — |  |  | 1 |  |  | — |  |  | — |  |  | (2) |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 11 |
Net (gain) loss | 28 |  |  | 8 |  |  | 12 |  |  | 3 |  |  | — |  |  | (1) |
Net periodic pension income | $ | (236) |  |  | $ | (65) |  |  | $ | (91) |  |  | $ | (11) |  |  | $ | (1) |  |  | $ | (4) |
Postretirement Benefits
Service cost | $ | 10 |  |  | $ | 3 |  |  | $ | 3 |  |  | $ | — |  |  | $ | — |  |  | $ | 1 |
Interest cost | 52 |  |  | 13 |  |  | 19 |  |  | 2 |  |  | — |  |  | 6 |
Expected return on plan assets | (68) |  |  | (26) |  |  | (25) |  |  | (1) |  |  | — |  |  | (7) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | 2 |  |  | — |  |  | 1 |  |  | — |  |  | — |  |  | — |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 5 |
Net gain | (11) |  |  | (2) |  |  | (2) |  |  | — |  |  | — |  |  | (6) |
Net periodic postretirement benefit cost (income) | $ | (15) |  |  | $ | (12) |  |  | $ | (4) |  |  | $ | 1 |  |  | $ | — |  |  | $ | (1) |
| Southern Company |  | Alabama Power |  | Georgia Power |  | Mississippi Power |  | Southern Power |  | Southern Company Gas
| (in millions)
Three Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |  |
Pension Plans
Service cost | $ | 73 |  |  | $ | 17 |  |  | $ | 18 |  |  | $ | 3 |  |  | $ | 2 |  |  | $ | 7 |
Interest cost | 159 |  |  | 37 |  |  | 47 |  |  | 7 |  |  | 2 |  |  | 11 |
Expected return on plan assets | (316) |  |  | (77) |  |  | (99) |  |  | (14) |  |  | (4) |  |  | (21) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | (1) |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 4 |
Net (gain) loss | 14 |  |  | 4 |  |  | 6 |  |  | — |  |  | (1) |  |  | — |
Net periodic pension income | $ | (70) |  |  | $ | (19) |  |  | $ | (28) |  |  | $ | (4) |  |  | $ | (1) |  |  | $ | — |
Postretirement Benefits |  |  |  |  |  |  |  |  |  |  |
Service cost | $ | 4 |  |  | $ | 1 |  |  | $ | 1 |  |  | $ | — |  |  | $ | — |  |  | $ | — |
Interest cost | 16 |  |  | 4 |  |  | 6 |  |  | 1 |  |  | — |  |  | 2 |
Expected return on plan assets | (22) |  |  | (9) |  |  | (8) |  |  | (1) |  |  | — |  |  | (2) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | 1 |  |  | — |  |  | 1 |  |  | — |  |  | — |  |  | — |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 2 |
Net (gain) loss | (4) |  |  | — |  |  | (3) |  |  | 1 |  |  | — |  |  | (1) |
Net periodic postretirement benefit cost (income) | $ | (5) |  |  | $ | (4) |  |  | $ | (3) |  |  | $ | 1 |  |  | $ | — |  |  | $ | 1 |
Nine Months Ended September 30, 2024 |  |  |  |  |  |  |  |  |  |
Pension Plans
Service cost | $ | 219 |  |  | $ | 51 |  |  | $ | 53 |  |  | $ | 9 |  |  | $ | 5 |  |  | $ | 21 |
Interest cost | 476 |  |  | 111 |  |  | 143 |  |  | 21 |  |  | 6 |  |  | 32 |
Expected return on plan assets | (947) |  |  | (230) |  |  | (296) |  |  | (43) |  |  | (12) |  |  | (64) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | — |  |  | — |  |  | 1 |  |  | — |  |  | — |  |  | (2) |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 11 |
Net loss | 41 |  |  | 12 |  |  | 15 |  |  | 2 |  |  | — |  |  | — |
Net periodic pension income | $ | (211) |  |  | $ | (56) |  |  | $ | (84) |  |  | $ | (11) |  |  | $ | (1) |  |  | $ | (2) |
Postretirement Benefits
Service cost | $ | 11 |  |  | $ | 3 |  |  | $ | 3 |  |  | $ | — |  |  | $ | — |  |  | $ | 1 |
Interest cost | 49 |  |  | 12 |  |  | 17 |  |  | 2 |  |  | — |  |  | 6 |
Expected return on plan assets | (66) |  |  | (26) |  |  | (24) |  |  | (1) |  |  | — |  |  | (6) |
Amortization: |  |  |  |  |  |  |  |  |  |  |
Prior service costs | 2 |  |  | — |  |  | 1 |  |  | — |  |  | — |  |  | — |
Regulatory asset | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 5 |
Net gain | (12) |  |  | (2) |  |  | (4) |  |  | — |  |  | — |  |  | (4) |
Net periodic postretirement benefit cost (income) | $ | (16) |  |  | $ | (13) |  |  | $ | (7) |  |  | $ | 1 |  |  | $ | — |  |  | $ | 2 |

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