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v3.22.2.2

Summary of Significant Accounting Policies - Property, Plant, and Equipment, and Depreciation (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020
Property, Plant, and Equipment, and Depreciation |  |  |
Depreciation | $ 1,800 | $ 1,400 | $ 1,600
Composite depreciation rate for completed plant | 2.98% | 2.28% | 2.74%
Reacquired Rights | $ 178 | $ 184 |
Amortization of Reacquired Rights | $ 6 | 8 | $ 8
Capitalized software amortization period | 7 years |  |
Accelerated depreciation | $ 140 | 136 | $ 125
Increase (decrease) in Year 1 due to new depreciation study | 345 |  |
Accumulated Amortization of Reacquired Rights | 42 | $ 36 |
Amortization Reacquired Rights, Year 1 | 6 |  |
Amortization Reacquired Rights, Year 2 | 6 |  |
Amortization Reacquired Rights, Year 3 | 6 |  |
Amortization Reacquired Rights, Year 4 | 6 |  |
Amortization Reacquired Rights, Year 5 | 6 |  |
Amortization Reacquired Rights, Year Thereafter | $ 148 |  |
Nuclear |  |  |
Property, Plant, and Equipment, and Depreciation |  |  |
Composite depreciation rate for completed plant | 2.72% | 2.38% | 2.38%
Coal-fired |  |  |
Property, Plant, and Equipment, and Depreciation |  |  |
Composite depreciation rate for completed plant | 4.27% | 1.95% | 3.62%
Hydroelectric |  |  |
Property, Plant, and Equipment, and Depreciation |  |  |
Composite depreciation rate for completed plant | 1.85% | 1.60% | 1.60%
Gas and oil-fired |  |  |
Property, Plant, and Equipment, and Depreciation |  |  |
Composite depreciation rate for completed plant | 3.38% | 2.98% | 3.04%
Transmission |  |  |
Property, Plant, and Equipment, and Depreciation |  |  |
Composite depreciation rate for completed plant | 1.51% | 1.34% | 1.34%
Other |  |  |
Property, Plant, and Equipment, and Depreciation |  |  |
Composite depreciation rate for completed plant | 3.64% | 7.12% | 7.26%

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