Arizona Public Service is seeking to add large amounts of renewables and battery storage during the next few years, along with hydrogen-capable natural gas combustion turbines.

The ask comes in APS’ 2023 Integrated Resource Plan (IRP) filed with the Arizona Corporation Commission.

Arizona’s largest utility is also choosing to refrain from exiting the Four Corners coal-fired power plant early, citing reliability concerns. APS studied retiring the 1.5 GW plant as early as 2027.

The utility said in part it “cannot responsibly support the early exit from Four Corners due to reliability concerns associated with the transition to newer, nascent technologies, as well as the lack of sufficient excess capacity resources in the Western United States…”

In its analysis of an early exit from Four Corners, APS found that any early exit scenario would be “heavily dependent” on transmission and natural gas availability, and the development timeframes for new generation would leave the grid too strained for too long.

APS plans to retire its other remaining coal plant, the Cholla Power Plant, by April 2025.

The utility is projecting a huge increase in energy demand over the next few years. APS customers use about 9,400 MW of electricity right now but will need 11,350 MW by 2027 and 13,000 MW by 2031, the utility said. Peak demand could grow by 40% during that time.

APS said it seeks to add more than 6,000 MW of solar and wind power, coupled with about 2,000 MW of battery storage, by 2027.

In the IRP, APS said its analysis demonstrated that hydrogen-capable gas turbines would complement renewables and storage in a least-cost portfolio. Even as renewables and storage are added, APS says it will need resources capable of “reliably meeting demand throughout the overnight period,” especially given the upcoming retirement of the Cholla Power Plant and the 2031 exit from Four Corners.

Once the two coal plants are no longer in the picture, APS says “significant gaps” will be left in both total energy produced and reliable summertime capacity. Quick-start, hydrogen-capable, natural gas resources could be co-sited at existing generation facilities, APS said, saving costs by reusing infrastructure.

APS’s full IRP can be read here.

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