XML 72 R50.htm IDEA: XBRL DOCUMENT
v3.21.2

Regulatory Matters - Cost Recovery Mechanisms (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 6 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Nov. 01, 2021 $ / kWh | Oct. 01, 2021 $ / kWh | Jun. 07, 2021 USD ($) | Jun. 01, 2021 USD ($) | Apr. 01, 2021 $ / kWh | Feb. 22, 2021 USD ($) | Feb. 15, 2021 USD ($) | Feb. 01, 2021 USD ($) $ / kWh | Aug. 20, 2020 USD ($) Customer | Jun. 01, 2020 USD ($) | May 01, 2020 $ / kWh | Feb. 14, 2020 USD ($) | Feb. 01, 2020 $ / kWh | Nov. 14, 2019 USD ($) Customer | Oct. 31, 2019 USD ($) | Oct. 29, 2019 USD ($) | Jun. 01, 2019 USD ($) | May 01, 2019 $ / kWh | Apr. 10, 2019 | Feb. 15, 2019 USD ($) | Feb. 01, 2019 $ / kWh | Aug. 13, 2018 USD ($) | Feb. 15, 2018 USD ($) | Feb. 01, 2018 $ / kWh | Jan. 08, 2018 USD ($) | Nov. 20, 2017 USD ($) | Sep. 01, 2017 USD ($) $ / kWh | Mar. 31, 2021 | Feb. 28, 2021 | Jun. 30, 2021 USD ($) | Jun. 30, 2020 USD ($) | Dec. 31, 2020 USD ($) program MW | Dec. 31, 2017 $ / kWh | Jul. 01, 2021 USD ($) | Jul. 01, 2020 USD ($) | May 15, 2020 USD ($) | May 05, 2020 USD ($) | Dec. 31, 2019 USD ($) | Jul. 01, 2019 USD ($) | Mar. 15, 2019 agreement | Dec. 31, 2018 USD ($) | Nov. 14, 2017 USD ($)
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 135,905,000 | $ 26,473,000 |  |  |  |  |  |  |  |  |  |  |
Amounts (charged) refunded to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (10,828,000) | 4,815,000 |  |  |  |  |  |  |  |  |  |  |
Rate plan comparison tool, number of customers | Customer |  |  |  |  |  |  |  |  | 3,800 |  |  |  |  | 13,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate plan comparison tool, inconvenience payment |  |  |  |  |  |  |  |  | $ 25 |  |  |  |  | $ 25 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 135,905,000 | 26,473,000 |  |  |  |  |  |  |  |  |  |  |
Amounts (charged) refunded to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (10,828,000) | 4,815,000 |  |  |  |  |  |  |  |  |  |  |
Percentage increase under PSA effective for first billing cycle beginning April 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Remaining percentage increase under PSA effective for first billing cycle beginning November 2021 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Demand side management funds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 36,000,000 |  |  |  |  |
Customer credits |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 43,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Customer credits, additional funds |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 7,000,000 |  |  |  |  |  |  |  |  |  |  |  |
APS | 2017 Settlement Agreement and its Customer Education and Outreach Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement amount |  |  |  |  |  | $ 24,750,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement amount returned to customers |  |  |  |  |  | $ 24,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lost Fixed Cost Recovery Mechanisms | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fixed cost recoverable per power lost (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.025 |  |  |  |  |  |  |  |  |
Percentage of retail revenues |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |  |  |  |  |  |  |
Amount of adjustment representing prorated sales losses pending approval |  |  |  |  |  |  | $ 38,500,000 |  |  |  |  | $ 26,600,000 |  |  |  |  |  |  |  | $ 36,200,000 |  |  | $ 60,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in amount of adjustment representing prorated sales losses |  |  |  |  |  |  | $ 11,800,000 |  |  |  |  | $ (9,600,000) |  |  |  |  |  |  |  | $ (24,500,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Program term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 18 years |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross-up for revenue requirement of rate regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (184,000,000) |  |  |  |  |  |  | $ 86,500,000 |  |  | $ 119,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
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 power capacity (in MW) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 80 |  |  |  |  |  |  |  |  |  |
ACC | RES | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Plan term |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |
ACC | RES 2018 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 93,100,000 | $ 84,700,000 |  |  |  | $ 86,300,000 |  |  |
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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2018 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 52,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 52,600,000
ACC | Demand Side Management Adjustor Charge 2019 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 34,100,000 |
ACC | Demand Side Management Adjustor Charge 2020 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 51,900,000 |  | $ 51,900,000 |  |  |  |
ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning balance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 175,835,000 | 70,137,000 | $ 70,137,000 |  |  |  |  |  |  |  |  |  |
Deferred fuel and purchased power costs — current period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 135,905,000 | 26,473,000 |  |  |  |  |  |  |  |  |  |  |
Amounts (charged) refunded to customers |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (10,828,000) | 4,815,000 |  |  |  |  |  |  |  |  |  |  |
Ending balance |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 300,912,000 | $ 101,425,000 | 175,835,000 |  |  |  |  |  |  |  |  |  |
PSA rate (in dollars per kWh) | $ / kWh |  |  |  |  | 0.001544 |  |  | 0.003544 |  |  |  |  | (0.000456) |  |  |  |  |  |  |  | 0.001658 |  |  | 0.004555 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate for prior year (in dollars per kWh) | $ / kWh |  |  |  |  | (0.004444) |  |  | 0.003434 |  |  |  |  | (0.002086) |  |  |  |  |  |  |  | 0.000536 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forward component of increase in PSA (in dollars per kWh) | $ / kWh |  |  |  |  | 0.005988 |  |  | 0.000110 |  |  |  |  | 0.001630 |  |  |  |  |  |  |  | 0.001122 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fuel and purchased power costs above annual cap |  |  |  |  |  |  |  | $ 215,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Net Metering | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost of service, resource comparison proxy method, maximum annual percentage decrease |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
First-year export energy price (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.129 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Second-year export energy price (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  |  |  |  | 0.094 |  |  |  |  |  |  | 0.105 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ACC | Demand Side Management Adjustor Charge 2021 | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of proposed budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 63,700,000 |  |  |  |  |  |  |  |  |  |
FERC | Environmental Improvement Surcharge | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in annual wholesale transmission rates |  |  |  |  |  |  |  | 10,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Rate matters, increase (decrease) in cost recovery, excess of annual amount |  |  |  |  |  |  |  | $ 1,500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
FERC | Open Access Transmission Tariff | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in annual wholesale transmission rates |  |  |  | $ 4,000,000 |  |  |  |  |  | $ (6,100,000) |  |  |  |  |  |  | $ 25,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in wholesale customer rates |  |  |  | (3,200,000) |  |  |  |  |  | 4,800,000 |  |  |  |  |  |  | 21,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in retail customer rates |  |  |  | 7,200,000 |  |  |  |  |  | (10,900,000) |  |  |  |  |  |  | 4,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in retail revenue requirements |  |  |  | $ (28,400,000) |  |  |  |  |  | $ (7,400,000) |  |  |  |  |  |  | $ 4,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost Recovery Mechanisms | ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Historical component of increase in PSA (in dollars per kWh) | $ / kWh |  |  |  |  |  |  |  | 0.004 |  |  |  |  | (0.002115) |  |  |  |  |  |  |  | (0.002897) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost recovery, number of agreements | agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |
Forecast | ACC | Power Supply Adjustor (PSA) | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate (in dollars per kWh) | $ / kWh | 0.003544 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PSA rate for prior year (in dollars per kWh) | $ / kWh | (0.004444) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forward component of increase in PSA (in dollars per kWh) | $ / kWh | 0.007988 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Forecast | ACC | Net Metering | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Second-year export energy price (in dollars per kWh) | $ / kWh |  | 0.105 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | ACC | APS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Change in regulatory asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating results |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (69,000,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | ACC | RES 2018 | APS | Solar Communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Required annual capital investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 10,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | ACC | RES 2018 | APS | Solar Communities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Settlement Agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Required annual capital investment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 15,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Amount of Adjustment Representing Prorated Sales Losses Pending Approval + References No definition available. + Details
Name: | pnw_AmountofAdjustmentRepresentingProratedSalesLossesPendingApproval
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Cost Recovery, Number Of Agreements + References No definition available. + Details
Name: | pnw_CostRecoveryNumberOfAgreements
Namespace Prefix: | pnw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- References No definition available. + Details
Name: | pnw_DeferredFuelAndPurchasedPowerRegulatoryAssetLiabilityRollForward
Namespace Prefix: | pnw_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Deferred Fuel and Purchased Power Regulatory Asset (Liability), Current + References No definition available. + Details
Name: | pnw_DeferredFuelandPurchasedPowerRegulatoryAssetLiabilityCurrent
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Forward Component of PSA Rate1 + References No definition available. + Details
Name: | pnw_ForwardComponentofPSARate1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Historical Component of PSA Rate1 + References No definition available. + Details
Name: | pnw_HistoricalComponentofPSARate1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amortization of deferred fuel and purchased power costs. + References No definition available. + Details
Name: | pnw_IncreaseDecreaseDeferredFuelAndPurchasedPowerAmortization
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Increase (Decrease) in Amount of Adjustment Representing Prorated Sales Losses + References No definition available. + Details
Name: | pnw_IncreaseDecreaseinAmountofAdjustmentRepresentingProratedSalesLosses
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Litigation Settlement, Amount Awarded to Customers + References No definition available. + Details
Name: | pnw_LitigationSettlementAmountAwardedToCustomers
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition PSA Rate1 + References No definition available. + Details
Name: | pnw_PSARate1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition PSA Rate In Prior Years1 + References No definition available. + Details
Name: | pnw_PSARateInPriorYears1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Number Of Programs + References No definition available. + Details
Name: | pnw_PublicUtilitiesNumberOfPrograms
Namespace Prefix: | pnw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Program Term + References No definition available. + Details
Name: | pnw_PublicUtilitiesProgramTerm
Namespace Prefix: | pnw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Requested Rate Increase (Decrease), Amount, One-time Bill Credit + References No definition available. + Details
Name: | pnw_PublicUtilitiesRequestedRateIncreaseDecreaseAmountOnetimeBillCredit
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Public Utilities, Requested Rate Increase (Decrease), Amount, One-time Bill Credit, Additional Benefit + References No definition available. + Details
Name: | pnw_PublicUtilitiesRequestedRateIncreaseDecreaseAmountOnetimeBillCreditAdditionalBenefit
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Public Utilities, Requested Rate Increase (Decrease), Deferred Taxes Amortization, Period + References No definition available. + Details
Name: | pnw_PublicUtilitiesRequestedRateIncreaseDecreaseDeferredTaxesAmortizationPeriod
Namespace Prefix: | pnw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Public Utilities, Requested Rate Increase (Decrease), Tax Cuts And Jobs Act of 2017, Income Tax Amount + References No definition available. + Details
Name: | pnw_PublicUtilitiesRequestedRateIncreaseDecreaseTaxCutsAndJobsActOf2017IncomeTaxAmount
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Public Utilities, Required Annual Capital Investment + References No definition available. + Details
Name: | pnw_PublicUtilitiesRequiredAnnualCapitalInvestment
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Public Utilities, Solar Power Capacity + References No definition available. + Details
Name: | pnw_PublicUtilitiesSolarPowerCapacity
Namespace Prefix: | pnw_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents information pertaining to cap percentage of retail revenues. + References No definition available. + Details
Name: | pnw_RateMatterCapPercentageOfRetailRevenue
Namespace Prefix: | pnw_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Rate Matter, Fixed Cost Recoverable Per Power Lost1 + References No definition available. + Details
Name: | pnw_RateMatterFixedCostRecoverablePerPowerLost1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition The period of time covered by a plan to implement a standard enacted by a regulatory authority. + References No definition available. + Details
Name: | pnw_RateMatterPlanTerm
Namespace Prefix: | pnw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the amount of proposed budget. + References No definition available. + Details
Name: | pnw_RateMatterProposedBudget
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Rate Matter, Request Second-Year Energy Price for Exported Energy1 + References No definition available. + Details
Name: | pnw_RateMatterRequestSecondYearEnergyPriceforExportedEnergy1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate Matter, Settlement Agreement, Energy Price for Exported Energy1 + References No definition available. + Details
Name: | pnw_RateMatterSettlementAgreementEnergyPriceforExportedEnergy1
Namespace Prefix: | pnw_
Data Type: | srt-types:perUnitItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate Matters, Amount Authorized To Be Collected + References No definition available. + Details
Name: | pnw_RateMattersAmountAuthorizedToBeCollected
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Matters, Cost of Service, Resource Comparison Proxy Method, Maximum Annual Percentage Decrease + References No definition available. + Details
Name: | pnw_RateMattersCostofServiceResourceComparisonProxyMethodMaximumAnnualPercentageDecrease
Namespace Prefix: | pnw_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate Matters, Cost of Service for Interconnected DG System Customers, Grandfathered Period + References No definition available. + Details
Name: | pnw_RateMattersCostofServiceforInterconnectedDGSystemCustomersGrandfatheredPeriod
Namespace Prefix: | pnw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate Matters, Cost of Service for New Customers, Guaranteed Export Price Period + References No definition available. + Details
Name: | pnw_RateMattersCostofServiceforNewCustomersGuaranteedExportPricePeriod
Namespace Prefix: | pnw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate Matters, Increase (Decrease) in Cost Recovery, Wholesale Customer Rates + References No definition available. + Details
Name: | pnw_RateMattersIncreaseDecreaseInCostRecoveryWholesaleCustomerRates
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Matters, Increase (Decrease) In Retail Revenue Requirements + References No definition available. + Details
Name: | pnw_RateMattersIncreaseDecreaseInRetailRevenueRequirements
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Matters, Increase (Decrease) in Cost Recovery + References No definition available. + Details
Name: | pnw_RateMattersIncreaseDecreaseinCostRecovery
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Matters, Increase (Decrease) in Cost Recovery, Excess Of Annual Amount + References No definition available. + Details
Name: | pnw_RateMattersIncreaseDecreaseinCostRecoveryExcessOfAnnualAmount
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Matters, Increase (Decrease) in Cost Recovery, Retail Customer Rates + References No definition available. + Details
Name: | pnw_RateMattersIncreaseDecreaseinCostRecoveryRetailCustomerRates
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Matters, Revenue Requirements + References No definition available. + Details
Name: | pnw_RateMattersRevenueRequirements
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Rate Plan Comparison Tool, Inconvenience Payment + References No definition available. + Details
Name: | pnw_RatePlanComparisonToolInconveniencePayment
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Rate Plan Comparison Tool, Number Of Customers + References No definition available. + Details
Name: | pnw_RatePlanComparisonToolNumberOfCustomers
Namespace Prefix: | pnw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Regulatory Clause, Deferred Fuel And Purchased Power Costs, Amount Above Annual Cap + References No definition available. + Details
Name: | pnw_RegulatoryClauseDeferredFuelAndPurchasedPowerCostsAmountAboveAnnualCap
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Regulatory Impact, Operating Results + References No definition available. + Details
Name: | pnw_RegulatoryImpactOperatingResults
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Regulatory Matters, Demand Side Management Funds + References No definition available. + Details
Name: | pnw_RegulatoryMattersDemandSideManagementFunds
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Regulatory Matters, Demand Side Management Funds, Customer Credits + References No definition available. + Details
Name: | pnw_RegulatoryMattersDemandSideManagementFundsCustomerCredits
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Regulatory Matters, Demand Side Management Funds, Customer Credits, Additional Funds + References No definition available. + Details
Name: | pnw_RegulatoryMattersDemandSideManagementFundsCustomerCreditsAdditionalFunds
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Regulatory Matters, Percentage Increase Due Under PSA In First Billing Cycle + References No definition available. + Details
Name: | pnw_RegulatoryMattersPercentageIncreaseDueUnderPSAInFirstBillingCycle
Namespace Prefix: | pnw_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Regulatory Matters, Remaining Percentage Increase Due Under PSA + References No definition available. + Details
Name: | pnw_RegulatoryMattersRemainingPercentageIncreaseDueUnderPSA
Namespace Prefix: | pnw_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The increase (decrease) during the reporting period in unrecovered fuel costs for a regulated utility company. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 + Details
Name: | us-gaap_IncreaseDecreaseInRegulatoryClauseRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount awarded to other party in judgment or settlement of litigation. + References No definition available. + Details
Name: | us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRateMattersApprovedAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=pnw_ArizonaPublicServiceCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_LitigationCaseAxis=pnw_A2017SettlementAgreementAndItsCustomerEducationAndOutreachPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_LostFixedCostRecoveryMechanismsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=pnw_ArizonaCorporationCommissionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_ArizonaRenewableEnergyStandardAndTariffMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_ArizonaRenewableEnergyStandardandTariff2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnw_PublicUtilityProgramAxis=pnw_SolarCommunitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_DemandSideManagementAdjustorCharge2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_DemandSideManagementAdjustorCharge2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_DemandSideManagementAdjustorCharge2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_PowerSupplyAdjustorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_NetMeteringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_DemandSideManagementAdjustorCharge2021Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=pnw_UnitedStatesFederalEnergyRegulatoryCommissionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_EnvironmentalImprovementSurchargeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=pnw_OpenAccessTransmissionTariffMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | pnw_PublicUtilitiesRegulatoryRegulatoryMattersAxis=pnw_CostRecoveryMechanismsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |