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Regulatory Matters - Cost Recovery Mechanisms (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |  |  |  |
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Mar. 10, 2023 USD ($) | Feb. 23, 2023 USD ($) $ / kWh | Feb. 01, 2023 USD ($) $ / kWh | Sep. 23, 2022 MW | Jul. 12, 2022 USD ($) $ / kWh | Jun. 01, 2022 USD ($) | Mar. 31, 2022 USD ($) MW | Feb. 15, 2022 USD ($) | Feb. 01, 2022 USD ($) $ / kWh $ / KWH_Kilowatt_hour | Nov. 01, 2021 $ / kWh | Oct. 01, 2021 $ / kWh | Jun. 07, 2021 USD ($) | Jun. 01, 2021 USD ($) | Apr. 01, 2021 $ / kWh | Feb. 15, 2021 USD ($) | Feb. 01, 2021 USD ($) $ / kWh | Aug. 20, 2020 USD ($) customer | Jul. 01, 2020 USD ($) | May 01, 2020 $ / kWh | Feb. 01, 2020 $ / kWh | Nov. 14, 2019 USD ($) customer | Oct. 31, 2019 $ / KWH_Kilowatt_hour | Oct. 29, 2019 USD ($) | May 01, 2019 $ / kWh | Apr. 10, 2019 | Aug. 13, 2018 USD ($) | Sep. 01, 2017 | Mar. 31, 2021 | Mar. 31, 2023 USD ($) | Mar. 31, 2022 USD ($) | Dec. 31, 2020 USD ($) program MW | Dec. 31, 2017 $ / kWh | Dec. 31, 2017 $ / KWH_Kilowatt_hour | Nov. 30, 2022 USD ($) | Jul. 01, 2022 USD ($) | Apr. 18, 2022 USD ($) | Dec. 31, 2021 USD ($) | Dec. 17, 2021 USD ($) | Dec. 09, 2021 USD ($) | Oct. 28, 2021 agreement | Jul. 01, 2021 USD ($) | May 15, 2020 USD ($) | May 05, 2020 USD ($) | Dec. 31, 2019 USD ($) | Mar. 15, 2019 agreement
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 90,305,000 | $ 6,110,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amounts charged to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (80,904,000) | (39,442,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate plan comparison tool, number of customers | customer |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,800 |  |  |  | 13,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate plan comparison tool, inconvenience payment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 25 |  |  |  | $ 25 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Demand side management funds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 36,000,000 |  |
Customer credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 43,000,000 |  |  |  |  |  |  |  |
Customer credits, additional funds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7,000,000 |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 90,305,000 | 6,110,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amounts charged to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (80,904,000) | (39,442,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage increase under PSA effective for first billing cycle beginning April 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remaining percentage increase under PSA effective for first billing cycle beginning November 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lost Fixed Cost Recovery Mechanisms | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed cost recoverable per power lost (in dollars per kWh) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.025 | 2.56 |  |  |  |  |  |  |  |  |  |  |  |
Percentage of retail revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of adjustment representing prorated sales losses pending approval |  |  |  |  |  |  |  | $ 59,100,000 |  |  |  |  |  |  | $ 38,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in amount of adjustment representing prorated sales losses |  |  |  |  |  |  |  | $ 32,500,000 |  |  |  |  |  |  | $ 11,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Program term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 18 years |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount requested to be returned in form of tax savings to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 86,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred taxes amortization, period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 28 years 6 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, one-time bill credit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 64,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, one-time bill credit, additional benefit |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 39,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of programs | program |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar capacity (in MW) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 80 |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | RES | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plan term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | RES 2018 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 84,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 86,200,000 |  |  |  | $ 100,500,000 |  | $ 93,100,000 |  |  |  |
Revenue requirements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorized amount to be collected |  |  |  |  |  |  |  |  |  |  |  | $ 68,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | RES 2018 | APS | Solar Communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Program term |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Retail Rate Case Filing with Arizona Corporation Commission | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial customers, market pricing, threshold | MW |  |  |  | 140 |  |  | 280 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2020 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 51,900,000 |  | $ 51,900,000 |
ACC | Net Metering | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service, resource comparison proxy method, maximum annual percentage decrease |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service for interconnected DG system customers, grandfathered period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service for new customers, guaranteed export price period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Second-year export energy price (in dollars per kWh) | $ / kWh |  |  |  |  | 0.0846 |  |  |  |  |  | 0.094 |  |  |  |  |  |  |  | 0.094 |  |  |  |  | 0.105 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2021 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 63,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2022 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 78,400,000 |  |  |  |  |  |  |
Increase in proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 14,000,000 |  |  |  |  |  |  |
ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 460,561,000 | 388,148,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 90,305,000 | 6,110,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amounts charged to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (80,904,000) | (39,442,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ending balance |  |  |  |  |  |  | $ 354,816,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 469,962,000 | $ 354,816,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate (in dollars per kWh) | $ / kWh |  | 0.019074 | 0.006 |  |  |  |  |  | 0.007544 | 0.003544 |  |  |  | 0.001544 |  | 0.003544 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate for prior year (in dollars per kWh) | $ / kWh |  | (0.005527) |  |  |  |  |  |  | 0.004842 | (0.004444) |  |  |  | (0.004444) |  | 0.003434 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forward component of increase in PSA (in dollars per kWh) | $ / kWh |  | 0.013071 |  |  |  |  |  |  | 0.012386 | 0.007988 |  |  |  | 0.005988 |  | 0.000110 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fuel and purchased power costs above annual cap |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 215,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Transition Component Of PSA Rate1 | $ / kWh |  | 0.011530 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Clause, Deferred Fuel And Purchased Power Costs, Balancing Account, Depletion Period |  | 24 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory Clause, Deferred Fuel And Purchased Power Costs, Balancing Account, Reporting Threshold Amount |  | $ 500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2023 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 88,000,000 |  |  |  |  |  |  |  |  |  |  |
FERC | Environmental Improvement Surcharge | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter, environmental surcharge cap rate (in dollars per kWh) | $ / KWH_Kilowatt_hour |  |  |  |  |  |  |  |  | 0.0005 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter, environmental surcharge cap rate amount | $ 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in annual wholesale transmission rates | (10,700,000) |  | $ 14,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matters, increase (decrease) in cost recovery, excess of annual amount | $ (7,500,000) |  | $ 3,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FERC | Open Access Transmission Tariff | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in annual wholesale transmission rates |  |  |  |  |  | $ 33,000,000 |  |  |  |  |  |  | $ 4,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decrease in wholesale customer rates |  |  |  |  |  | 6,400,000 |  |  |  |  |  |  | 3,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in retail customer rates |  |  |  |  |  | (26,600,000) |  |  |  |  |  |  | 7,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in retail revenue requirements |  |  |  |  |  | $ (2,400,000) |  |  |  |  |  |  | $ (28,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum increase decrease in PSA rate | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.004 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Historical component of increase in PSA (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  | 0.004 |  |  |  |  |  |  | 0.004 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost recovery, number of agreements | agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  | 2
Minimum | ACC | RES 2018 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorized spending |  |  |  |  | $ 20,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | ACC | RES 2018 | APS | Solar Communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Required annual capital investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | FERC | Environmental Improvement Surcharge | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter, environmental surcharge cap rate amount |  |  |  |  |  |  |  |  | $ 13,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Retail Rate Case Filing with Arizona Corporation Commission | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed cost recoverable per power lost (in dollars per kWh) | $ / KWH_Kilowatt_hour |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.68 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | ACC | RES 2018 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Authorized spending |  |  |  |  | $ 30,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | ACC | RES 2018 | APS | Solar Communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Required annual capital investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 15,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | FERC | Environmental Improvement Surcharge | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matter, environmental surcharge cap rate amount |  |  |  |  |  |  |  |  | $ 15,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Damage from Fire, Explosion or Other Hazard | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Past due balance threshold qualifying for payment extension |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 75 |  |  |  |  |  |  |  |  |

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