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Regulatory Matters - Capital Structure and Costs of Capital (Details) - $ / kWh | Oct. 01, 2021 | May 01, 2020 | Oct. 31, 2019 | May 01, 2019 | May 01, 2018
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Cost of Capital |  |  |  |  |
Long-term debt |  |  | 4.10% |  |
Common stock equity |  |  | 10.15% |  |
Weighted-average cost of capital |  |  | 7.41% |  |
Retail Rate Case Filing with Arizona Corporation Commission | APS |  |  |  |  |
Capital Structure |  |  |  |  |
Common stock equity |  |  | 54.70% |  |
Retail Rate Case Filing with Arizona Corporation Commission | ACC | APS |  |  |  |  |
Capital Structure |  |  |  |  |
Long-term debt |  |  | 45.30% |  |
Net Metering | ACC | APS |  |  |  |  |
Cost of Capital |  |  |  |  |
Second-year export energy price (in dollars per kWh) |  | 0.094 |  | 0.105 | 0.116
Net Metering | ACC | APS | Forecast |  |  |  |  |
Cost of Capital |  |  |  |  |
Second-year export energy price (in dollars per kWh) | 10.5 |  |  |  |

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