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BENEFIT PLANS (Tables) | 9 Months Ended
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Sep. 30, 2025
Retirement Benefits [Abstract] |
Components of Net Periodic Benefit Cost | Pension Plans
Three Months Ended September 30, 2025 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 23.9 |  |  | $ | 2.2 |  |  | $ | 2.3 |  |  | $ | 3.2 |  |  | $ | 2.2 |  |  | $ | 1.5 |  |  | $ | 1.9 |
Interest Cost |  | 52.9 |  |  | 4.4 |  |  | 6.2 |  |  | 6.2 |  |  | 4.9 |  |  | 2.5 |  |  | 3.2 |
Expected Return on Plan Assets |  | (70.3) |  |  | (5.6) |  |  | (9.4) |  |  | (9.7) |  |  | (7.3) |  |  | (3.8) |  |  | (3.7) |
Amortization of Net Actuarial Loss |  | 4.1 |  |  | 0.3 |  |  | 0.5 |  |  | 0.4 |  |  | 0.4 |  |  | 0.3 |  |  | 0.2 |
Net Periodic Benefit Cost (Credit) |  | $ | 10.6 |  |  | $ | 1.3 |  |  | $ | (0.4) |  |  | $ | 0.1 |  |  | $ | 0.2 |  |  | $ | 0.5 |  |  | $ | 1.6 |
Three Months Ended September 30, 2024 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 25.6 |  |  | $ | 2.3 |  |  | $ | 2.4 |  |  | $ | 3.3 |  |  | $ | 2.3 |  |  | $ | 1.5 |  |  | $ | 1.9 |
Interest Cost |  | 51.9 |  |  | 4.4 |  |  | 6.2 |  |  | 5.9 |  |  | 4.8 |  |  | 2.5 |  |  | 3.1 |
Expected Return on Plan Assets |  | (80.2) |  |  | (6.5) |  |  | (10.7) |  |  | (10.7) |  |  | (8.2) |  |  | (4.3) |  |  | (4.4) |
Amortization of Net Actuarial Loss |  | 1.0 |  |  | — |  |  | 0.1 |  |  | 0.1 |  |  | 0.1 |  |  | — |  |  | 0.1 |
Net Periodic Benefit Cost (Credit) (a) |  | $ | (1.7) |  |  | $ | 0.2 |  |  | $ | (2.0) |  |  | $ | (1.4) |  |  | $ | (1.0) |  |  | $ | (0.3) |  |  | $ | 0.7 |
Nine Months Ended September 30, 2025 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 71.8 |  |  | $ | 6.6 |  |  | $ | 6.9 |  |  | $ | 9.5 |  |  | $ | 6.8 |  |  | $ | 4.5 |  |  | $ | 5.7 |
Interest Cost |  | 158.5 |  |  | 13.2 |  |  | 18.7 |  |  | 18.6 |  |  | 14.6 |  |  | 7.7 |  |  | 9.4 |
Expected Return on Plan Assets |  | (210.8) |  |  | (16.7) |  |  | (28.2) |  |  | (29.1) |  |  | (22.0) |  |  | (11.5) |  |  | (11.0) |
Amortization of Net Actuarial Loss |  | 12.2 |  |  | 1.0 |  |  | 1.4 |  |  | 1.3 |  |  | 1.1 |  |  | 0.6 |  |  | 0.7 |
Net Periodic Benefit Cost (Credit) |  | $ | 31.7 |  |  | $ | 4.1 |  |  | $ | (1.2) |  |  | $ | 0.3 |  |  | $ | 0.5 |  |  | $ | 1.3 |  |  | $ | 4.8 |
Nine Months Ended September 30, 2024 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 76.8 |  |  | $ | 6.7 |  |  | $ | 7.3 |  |  | $ | 9.9 |  |  | $ | 7.0 |  |  | $ | 4.6 |  |  | $ | 5.9 |
Interest Cost |  | 155.7 |  |  | 13.1 |  |  | 18.6 |  |  | 17.8 |  |  | 14.2 |  |  | 7.5 |  |  | 9.3 |
Expected Return on Plan Assets |  | (240.6) |  |  | (19.5) |  |  | (32.1) |  |  | (32.1) |  |  | (24.5) |  |  | (13.0) |  |  | (13.2) |
Amortization of Net Actuarial Loss |  | 3.2 |  |  | 0.2 |  |  | 0.3 |  |  | 0.3 |  |  | 0.2 |  |  | 0.1 |  |  | 0.2 |
Net Periodic Benefit Cost (Credit) (a) |  | $ | (4.9) |  |  | $ | 0.5 |  |  | $ | (5.9) |  |  | $ | (4.1) |  |  | $ | (3.1) |  |  | $ | (0.8) |  |  | $ | 2.2 |
(a)Excludes an immaterial settlement amount to a non-qualified pension plan in the second quarter of 2024 for AEP. See Note 12 - Voluntary Severance Program for additional information. OPEB
Three Months Ended September 30, 2025 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 0.9 |  |  | $ | — |  |  | $ | — |  |  | $ | — |  |  | $ | 0.1 |  |  | $ | 0.1 |  |  | $ | 0.1 |
Interest Cost |  | 8.5 |  |  | 0.7 |  |  | 1.4 |  |  | 1.0 |  |  | 0.8 |  |  | 0.4 |  |  | 0.5 |
Expected Return on Plan Assets |  | (28.2) |  |  | (2.3) |  |  | (4.1) |  |  | (3.4) |  |  | (2.9) |  |  | (1.6) |  |  | (1.9) |
Amortization of Prior Service Credit |  | (0.6) |  |  | — |  |  | (0.1) |  |  | — |  |  | (0.1) |  |  | — |  |  | — |
Amortization of Net Actuarial Gain |  | (0.3) |  |  | — |  |  | (0.1) |  |  | — |  |  | — |  |  | — |  |  | — |
Net Periodic Benefit Credit |  | $ | (19.7) |  |  | $ | (1.6) |  |  | $ | (2.9) |  |  | $ | (2.4) |  |  | $ | (2.1) |  |  | $ | (1.1) |  |  | $ | (1.3) |
Three Months Ended September 30, 2024 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 1.1 |  |  | $ | — |  |  | $ | 0.2 |  |  | $ | 0.1 |  |  | $ | — |  |  | $ | 0.1 |  |  | $ | 0.1 |
Interest Cost |  | 10.3 |  |  | 0.9 |  |  | 1.7 |  |  | 1.2 |  |  | 1.1 |  |  | 0.6 |  |  | 0.7 |
Expected Return on Plan Assets |  | (27.8) |  |  | (2.3) |  |  | (4.1) |  |  | (3.4) |  |  | (3.0) |  |  | (1.5) |  |  | (1.9) |
Amortization of Prior Service Credit |  | (3.1) |  |  | (0.3) |  |  | (0.5) |  |  | (0.4) |  |  | (0.3) |  |  | (0.2) |  |  | (0.3) |
Amortization of Net Actuarial Loss |  | 0.8 |  |  | 0.1 |  |  | 0.1 |  |  | 0.1 |  |  | 0.1 |  |  | — |  |  | 0.1 |
Net Periodic Benefit Credit (a) |  | $ | (18.7) |  |  | $ | (1.6) |  |  | $ | (2.6) |  |  | $ | (2.4) |  |  | $ | (2.1) |  |  | $ | (1.0) |  |  | $ | (1.3) |
Nine Months Ended September 30, 2025 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 2.7 |  |  | $ | 0.2 |  |  | $ | 0.3 |  |  | $ | 0.3 |  |  | $ | 0.3 |  |  | $ | 0.2 |  |  | $ | 0.2 |
Interest Cost |  | 25.7 |  |  | 2.0 |  |  | 4.1 |  |  | 2.9 |  |  | 2.5 |  |  | 1.3 |  |  | 1.6 |
Expected Return on Plan Assets |  | (84.7) |  |  | (7.0) |  |  | (12.3) |  |  | (10.1) |  |  | (8.8) |  |  | (4.6) |  |  | (5.7) |
Amortization of Prior Service Credit |  | (1.8) |  |  | (0.1) |  |  | (0.3) |  |  | (0.2) |  |  | (0.2) |  |  | (0.1) |  |  | (0.1) |
Amortization of Net Actuarial Gain |  | (0.9) |  |  | — |  |  | (0.3) |  |  | — |  |  | — |  |  | — |  |  | — |
Net Periodic Benefit Credit |  | $ | (59.0) |  |  | $ | (4.9) |  |  | $ | (8.5) |  |  | $ | (7.1) |  |  | $ | (6.2) |  |  | $ | (3.2) |  |  | $ | (4.0) |
Nine Months Ended September 30, 2024 |  | AEP |  | AEP Texas |  | APCo |  | I&M |  | OPCo |  | PSO |  | SWEPCo
|  | (in millions)
Service Cost |  | $ | 3.3 |  |  | $ | 0.2 |  |  | $ | 0.4 |  |  | $ | 0.4 |  |  | $ | 0.2 |  |  | $ | 0.2 |  |  | $ | 0.3 |
Interest Cost |  | 31.4 |  |  | 2.5 |  |  | 5.0 |  |  | 3.6 |  |  | 3.2 |  |  | 1.7 |  |  | 2.0 |
Expected Return on Plan Assets |  | (83.5) |  |  | (6.8) |  |  | (12.2) |  |  | (10.1) |  |  | (8.9) |  |  | (4.5) |  |  | (5.6) |
Amortization of Prior Service Credit |  | (9.5) |  |  | (0.8) |  |  | (1.4) |  |  | (1.3) |  |  | (0.9) |  |  | (0.6) |  |  | (0.8) |
Amortization of Net Actuarial Loss |  | 2.3 |  |  | 0.2 |  |  | 0.3 |  |  | 0.3 |  |  | 0.3 |  |  | 0.1 |  |  | 0.2 |
Net Periodic Benefit Credit (a) |  | $ | (56.0) |  |  | $ | (4.7) |  |  | $ | (7.9) |  |  | $ | (7.1) |  |  | $ | (6.1) |  |  | $ | (3.1) |  |  | $ | (3.9) |
(a)Excludes an immaterial amount related to special termination benefits resulting from the voluntary severance program announced in the second quarter of 2024. See Note 12 - Voluntary Severance Program for additional information.
Qualified Pension Contribution | The following table provides details of the contribution by Registrant:
Company |  | Qualified Pension Plan
|  | (in millions)
AEP |  | $ | 94.7 |
AEP Texas |  | 12.0 |
APCo |  | 0.4 |
I&M |  | 2.1 |
PSO |  | 1.4 |
SWEPCo |  | 8.8 |

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