Rate Regulation Summary | 2019 Rate Case | 2022 Rate Case | Adjustment Mechanisms | Federal Regulation

Rate Regulation Summary

Detailed Information On Regulatory Matters

Regulatory developments are discussed in detail in a number of sections of the 2021 Annual Report on Form 10-K for Pinnacle West and APS. See "Current and Future Resources" and "Competitive Environment and Regulatory Oversight" in Item 1; "Regulatory Overview" in Management's Discussion and Analysis of Financial Condition and Results of Operations in Item 7; and Note 3 of Combined Notes to Consolidated Financial Statements, "Regulatory Matters," in 
Item 8.

State Regulation

The Arizona Corporation Commission (ACC) regulates APS's retail electric rates and its issuance of securities. The ACC also must approve any transfer of APS's property used to provide retail electric service and must approve or receive prior notification of certain transactions between APS, Pinnacle West and their respective affiliates.

ACC Organization

The ACC consists of five elected commissioners with staggered terms. The terms are four years each, with a limit of two consecutive terms in office. Mid-term vacancies (due to resignation, etc.) are filled by appointment of the Governor to serve until the next general election.

Commissioner Current Term
Commissioner Since Expires
James O'Connor (Rep.) (Chairman) January 2021 January 2025
Lea Marquez-Peterson (Rep.) May 2019 January 2025
Nick Myers (Rep.) January 2023 January 2027
Kevin Thompson (Rep.) January 2023 January 2027
Anna Tovar (Dem.) January 2021 January 2025

Test Period

A historical test period is required by ACC rule; however, the ACC has discretion to consider certain matters subsequent to the end of the historical year.

Retail Base Rate Changes (and Interim Adjustments)

The table below shows APS's net retail base rate changes since 2012 ($ in millions):

Type Effective Date(s) Revenue
Base Rate Decrease December 1, 2021 ($120)*
Base Rate Increase August 19, 2017 $ 95
Base Rate Increase July 1, 2012 $ -

* Total bill decrease of $4.8 million, including the effect of adjustors, but excluding temporary Coal Community Transition impacts

2019 Rate Case

On November 2, 2021, the Arizona Corporation Commission (ACC) voted on the APS 2019 rate case following multiple days of contentious deliberation. The decision contains numerous elements that are problematic, including: 

  • A total bill decrease of $4.8 million, including the effect of adjustors; 
  • Disallowance of a portion of the Four Corners Power Plant emission control assets of $216 million in a wrongful application of the state’s well-established standard of prudence; and
  • A cut in the company’s return on equity from 10 percent to 8.7 percent – the lowest for any mid- to large-sized vertically integrated, investor-owned utility in the U.S. with 2020-2021 rate case results. 

In December 2021, APS filed its Notice of Direct Appeal at the Arizona Court of Appeals. In March 2023, the Court vacated the 20-basis-point penalty and the disallowance of $216 million of APS’s Four Corners SCR investment. The Court remanded the issue to the ACC for further proceedings. In June 2023, the ACC and APS agreed to a resolution, which includes the new Court Resolution Surcharge to recover these costs:

  • 1. Investment related to the installation of the emissions equipment at the Four Corners Power Plant.
  • 2. Authorized ROE is now 8.9%.
  • 3. APS’s lost revenue between December 2021 and June 2023 related to these two items.

A copy of the order is available at

You can review the final decision and other materials related to the rate case using the e-docket function on the ACC website. Search for docket no. E-01345A-19-0236.

2022 Rate Case

APS filed an application with the ACC on October 28, 2022 seeking an increase in annual retail base rates. Rebuttal testimony in July 2023 reflected a revenue requirement of approximately $383 million, with an average annual customer bill impact of 11.3%. APS requested that the increase become effective December 1, 2023. The hearing for this rate case is scheduled to begin in August 2023. APS cannot predict the outcome of its request.

View the related 8-K and news release.


Direct Testimony

Rebuttal Testimony

Rejoinder Testimony

You can find additional documents related to this rate case on or on the ACC’s website (docket #E-01345A-22-0144).

Adjustment Mechanisms

APS has received supportive regulatory decisions that allow for more timely recovery of certain costs through the following recovery mechanisms.

Transmission Cost Adjustor (TCA)

APS recovers annual changes in federally determined charges for transmission services to serve retail customers through the TCA. See “Federal Regulation” for additional details on FERC formula-based rates and the TCA.

Power Supply Adjustor (PSA)

The PSA was initially approved by the ACC in 2005 and most recently modified in 2017. The mechanism provides for the adjustment of retail rates to reflect variations in retail fuel and purchased power costs, subject to specified parameters and procedures. See page 8 of the 2021 Statistical Report for a summary of historical PSA balances and activity.

Deferrals – Beginning July 1, 2012, APS defers for recovery or refund 100% of the difference between actual retail fuel and purchased power costs (as defined) and the Base Fuel Rate. From April 2005 through June 2012, APS deferred 90% of the difference between actual retail fuel and purchased power costs (as defined) and the Base Fuel Rate. The table below summarizes the Base Fuel Rates determined in APS's rate cases and approved by the ACC (per kWh):

Effective Dates Base Fuel Rate*
December 2021 onward $ 0.0315
August 2017 - November 2021 $ 0.0302
July 2012 - August 2017 $ 0.0321
January 2010 - June 2012 $ 0.0376
July 2007 - December 2009 $ 0.0325
April 2005 - June 2007 $ 0.0207

* Numbers are rounded

Recovery – The PSA rate is adjusted annually each February 1 (unless otherwise approved by the ACC). The PSA rate includes (a) a “Forward Component,” under which APS recovers or refunds differences between expected fuel and purchased power costs for the upcoming PSA year and those embedded in the Base Fuel Rate; (b) a “Historical Component,” under which differences between actual fuel and purchased power costs and those recovered through the combination of the Base Fuel Rate and the Forward Component are recovered during the next PSA Year; and (c) a “Transition Component,” under which APS may seek mid-year PSA rate changes due to large variances between actual fuel and purchased power costs and the combination of the Base Fuel Rate and the Forward Component.

Demand Side Management Adjustment Clause (DSMAC)

The Commission's Energy Efficiency Standard requires APS to submit an annual DSM implementation plan, including estimated amounts for program costs, for review by and approval of the ACC. In order to recover these estimated amounts for use on certain demand-side management programs, a surcharge is added to customer bills similar to that described above under the RES. The EES allows for the recovery of energy efficiency program expenses and any earned incentives. In June 2021, the ACC adopted clean energy rules package and additional procedural steps in the rulemaking process were required to be completed before the rules were to take effect. On January 26, 2022, the ACC reversed its prior decision and declined to send the final rules package through the rulemaking process. Instead, the ACC opened a new docket to consider all-source requests for proposal requirements and the Integrated Resource Planning process.

Tax Expense Adjustment Mechanism (TEAM)

As part of the 2017 Settlement Agreement, APS established a rate adjustment mechanism that enables the pass-through of certain income tax effects to customers as a result of the Tax Cuts and Jobs Act effective January 1, 2018. APS implemented the TEAM in three phases from March 2018 through December 2021, providing more than $245 million in annual tax reductions back to customers. At the conclusion of the Company's 2019 rate case, beginning in December 2021, these reductions were moved into base rates and the adjustor was set to zero, but the mechanism remains available to respond to any future tax changes.

Renewable Energy Adjustment Charge (REAC)

In 2006, the ACC adopted the Renewable Energy Standard (RES). Under the RES, electric utilities that are regulated by the ACC must supply an increasing percentage of their retail electric energy sales from eligible renewable resources, including solar, wind, biomass, biogas and geothermal technologies, up to 15% of calendar-year retail sales by 2025. In order to achieve these requirements, the ACC allows APS to include a REAC as part of customer bills to recover approved renewable energy project expenses. Each year, APS is required to file a five-year implementation plan with the ACC and seek approval for funding the upcoming year’s RES budget.

Lost Fixed Cost Recovery (LFCR)

The LFCR mechanism permits APS to recover on an after-the-fact basis a portion of its fixed costs that would otherwise have been collected by APS in the kWh sales lost due to APS energy efficiency (EE) programs and to distributed generation (DG) such as rooftop solar arrays. The fixed costs recoverable by the LFCR mechanism established in the 2017 Settlement Agreement was approximately 2.5 cents per residential and non-residential kWh lost. The LFCR adjustment has a year-over-year cap of 1% of retail revenues. Any amounts left unrecovered in a particular year because of this cap can be carried over for recovery in a future year. The kWh lost from energy efficiency are based on a third-party evaluation of APS’s EE programs. DG sales losses are determined from the metered output from the DG units or if metering is unavailable, through accepted estimating techniques.

As a result of the 2019 Rate Case decision, APS’s annual LFCR adjustor rate will be dependent on an annual earnings test filing, which will compare APS’s previous year’s rate of return with the related authorized rate of return. If the actual rate of return is higher than the authorized rate of return, the LFCR rate for the subsequent year is set at zero.

Environmental Improvement Surcharge (EIS)

The Environmental Improvement Surcharge allows for the recovery of carrying costs for capital expenditures associated with government-mandated environmental controls, subject to an existing cents per kWh cap on cost recovery. The cap was increased to recover up to approximately $14 million annually with the approval of the 2017 Settlement Agreement.

Federal Regulation

APS is subject to regulation by the U.S. Federal Energy Regulatory Commission (FERC) in certain matters which include wholesale power sales and transmission services. The FERC is composed of five commissioners who are appointed by the President, approved by Congress and serve five-year terms.

The FERC continues to address issues related to standard market design for wholesale markets, regional transmission organizations to support non-discriminatory markets, and other issues related to restructuring wholesale power markets. APS is an active participant in these proceedings.

Formula Transmission Tariff and Retail Transmission Cost Adjustor

In July 2008, FERC approved an Open Access Transmission Tariff for APS to move from fixed rates to a formula rate-setting methodology in order to more accurately reflect and recover the costs that APS incurs in providing transmission services. A large portion of the rate represents charges for transmission services to serve APS’s retail customers (Retail Transmission Charges). In order to recover the Retail Transmission Charges, APS was previously required to file an application with, and obtain approval from, the ACC to reflect changes in Retail Transmission Charges through the TCA. Under the terms of the 2012 Settlement Agreement, however, an adjustment to rates to recover the Retail Transmission Charges will be made annually each June 1 and will go into effect automatically. Also, with the approval of the 2017 Settlement Agreement, a balancing account was added to the TCA. In May 2018, FERC approved modifications to the Formula Rate to: (1) reflect the reduced federal income tax rate resulting from the Tax Cuts and Jobs Act of 2017 ("TCJA"); (2) reclassify the excess accumulated deferred income taxes resulting from the federal income tax reduction from accumulated deferred income taxes to a regulatory asset and regulatory liability; and (3) provide transmission customers the future benefit of amortization of the excess accumulated deferred income taxes regulatory liability. The formula rate is updated each year effective June 1 on the basis of APS’s actual cost of service, as disclosed in APS’s FERC Form 1 report for the previous fiscal year.

The table below summarizes APS's transmission rate changes:

Annual Increase / (Decrease) ($ Millions)
Effective Date Retail Portion Wholesale Portion Total
June 1, 2021* 7 (3) 4
June 1, 2020 (11) 5 (6)
June 1, 2019 5 21 26
June 1, 2018 (27) 4 (23)
June 1, 2017 37 (2) 35
June 1, 2016 25 - 25
June 1, 2015 (7) (11) (18)
June 1, 2014 5 1 6
June 1, 2013 21 5 26

* Since changes in retail transmission charges are reflected through the TCA after consideration of 
 transmission recovery in retail base rates and the ACC approved balancing account, the retail revenue
 requirement decreased by $28.4 million, resulting in reductions to both residential and commercial rates.

Email Alerts


Enter the code shown above.