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RATE MATTERS - Regulatory Assets Pending Final Approval (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | --- | ---
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | $ 4,950.2 |  | $ 5,129.2
Regulatory assets, current | 380.6 |  | 445.9
AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 396.3 |  | 353.6
APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 1,498.9 |  | 1,366.0
Regulatory assets, current | 79.3 |  | 148.1
Regulatory asset, requested to be financed through securitization | 2,527.6 |  |
I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 620.4 |  | 548.1
Regulatory assets, current | 0.0 |  | 10.6
OPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 347.6 |  | 379.1
PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 603.5 |  | 527.8
Regulatory assets, current | 22.3 |  | 64.7
SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 922.2 |  | 921.3
Regulatory assets, current | 106.7 |  | 106.6
West Virginia | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Regulatory asset, requested to be financed through securitization |  | $ 2,400.0 |
Total Regulatory Assets Pending Final Regulatory Approval |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 1,492.5 |  | 1,348.0
Total Regulatory Assets Pending Final Regulatory Approval | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 156.9 |  | 77.1
Total Regulatory Assets Pending Final Regulatory Approval | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 572.6 |  | 535.5
Total Regulatory Assets Pending Final Regulatory Approval | I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 111.7 |  | 115.0
Total Regulatory Assets Pending Final Regulatory Approval | OPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 0.9 |  | 0.5
Total Regulatory Assets Pending Final Regulatory Approval | PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 70.7 |  | 30.3
Total Regulatory Assets Pending Final Regulatory Approval | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 551.3 |  | 491.4
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 206.2 |  | 168.6
Welsh Plant, Units 1 and 3 Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 206.2 |  | 168.6
Pirkey Plant Accelerated Depreciation | Regulatory Assets Currently Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 134.1 |  | 121.3
Pirkey Plant Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 134.1 |  | 121.3
Storm-Related Costs | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Regulatory asset, requested to be financed through securitization | 157.9 |  |
Storm-Related Costs | West Virginia | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Regulatory asset, requested to be financed through securitization |  | $ 118.0 |
Storm-Related Costs | Regulatory Assets Currently Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 53.5 |  | 51.0
Storm-Related Costs | Regulatory Assets Currently Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 41.3 |  | 41.3
Storm-Related Costs | Regulatory Assets Currently Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 12.2 |  | 9.7
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 202.2 |  | 300.8
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 34.4 |  | 13.1
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 49.6 |  | 144.2
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 29.3 |  | 6.3
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 22.4 |  | 4.9
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 44.9 |  | 39.9
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia |  |  |
Regulatory Asset [Line Items] |  |  |
Regulatory asset, requested to be financed through securitization | 40.0 |  |
Storm-Related Costs | Regulatory Assets Currently Not Earning a Return | West Virginia | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Regulatory asset, requested to be financed through securitization | 40.0 |  |
Unrecovered Winter Storm Fuel Costs | Regulatory Assets Currently Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 47.2 |  | 70.7
Unrecovered Winter Storm Fuel Costs | Regulatory Assets Currently Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 47.2 |  | 70.7
Regulatory assets, current | 37.0 |  | 37.0
Unified Tracking Mechanism Deferred Costs | Regulatory Assets Currently Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 39.2 |  | 0.0
Unified Tracking Mechanism Deferred Costs | Regulatory Assets Currently Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 39.2 |  | 0.0
System Resiliency Plan Deferred Costs | Regulatory Assets Currently Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 8.6 |  | 0.0
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 30.9 |  | 20.7
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 1.5 |  | 1.1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 3.3 |  | 6.4
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | OPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 0.9 |  | 0.4
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 4.3 |  | 1.1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 130.8 |  | 86.3
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 2.9 |  | 1.3
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 20.7 |  | 11.9
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 1.7 |  | 1.6
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | OPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 0.0 |  | 0.1
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 7.8 |  | 1.2
Other Regulatory Assets Pending Final Regulatory Approval | Regulatory Assets Currently Not Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 19.5 |  | 18.7
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 386.5 |  | 357.4
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 305.8 |  | 282.1
Plant Retirement Costs – Asset Retirement Obligation Costs | Regulatory Assets Currently Not Earning a Return | I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 77.4 |  | 74.0
2024-2025 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 166.0 |  | 78.4
2024-2025 Virginia Biennial Under-Earnings | Regulatory Assets Currently Not Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 166.0 |  | 78.4
NOLC Costs | Regulatory Assets Currently Not Earning a Return |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 95.9 |  | 92.8
NOLC Costs | Regulatory Assets Currently Not Earning a Return | I&M |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 0.0 |  | 26.7
NOLC Costs | Regulatory Assets Currently Not Earning a Return | PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 25.4 |  | 16.4
NOLC Costs | Regulatory Assets Currently Not Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 70.5 |  | 49.6
Deferred Pension and OPEB Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 24.7 |  | 15.6
Line Inspection Costs | Regulatory Assets Currently Not Earning a Return | AEP Texas |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 5.8 |  | 5.8
Pension Settlement | Regulatory Assets Currently Not Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 16.7 |  | 17.8
Pension Settlement | Regulatory Assets Currently Not Earning a Return | PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 7.4 |  | 7.8
Virginia Retail Consumables Deferral | Regulatory Assets Currently Not Earning a Return | APCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 12.3 |  | 0.0
Generation PBA and Delayed Retirement Deferral | Regulatory Assets Currently Not Earning a Return | PSO |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | 7.7 |  | 0.0
Dolet Hills Power Station Accelerated Depreciation | Regulatory Assets Currently Earning a Return | SWEPCo |  |  |
Regulatory Asset [Line Items] |  |  |
Noncurrent Regulatory Assets | $ 12.4 |  | $ 11.8

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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + 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 + Details
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