Arizona Public Service plans to convert two closed coal units at its Cholla Power Plant to run on natural gas, adding 380 MW of generation. Construction would start in 2028 and the units would come online the year after, pending state approval.
Arizona Public Service will convert two retired coal-fired units at its Cholla Power Plant to burn natural gas, making the most of existing infrastructure at the site. The utility said construction would begin in 2028, with the 380-MW units coming online the following year. State regulators still need to approve the plan.
Why APS is choosing gas
Rising power demand across the utility's service territory drove the decision. APS said the need for more electricity pushed it to move forward with the conversion, having earlier chosen to wait until it could show gas-fired generation would benefit customers.
The company framed natural gas as an around-the-clock resource that fits existing plans. On its website, APS wrote that "natural gas is critical to deliver reliable service for all customers" as Arizona demand grows, describing it as flexible, on-demand power. The utility also pointed to a diverse mix spanning nuclear, natural gas, solar, wind, battery energy storage and coal.
Reusing the Cholla site
Building at an existing plant keeps costs down. APS said very little new transmission infrastructure would be needed, with most work upgrading existing equipment rather than laying new lines. A lateral line, a smaller-diameter pipeline, will connect the site to an existing natural gas pipeline system, and the old coal-burning equipment will be removed.
The Cholla plant, located in Joseph City in northeastern Arizona, entered commercial operation in 1962 and once ran as a 1.02-GW coal facility jointly owned by APS and PacifiCorp. Its last operating units stopped burning coal in March 2025, a shutdown APS tied to federal Regional Haze Program rules that required an end to coal burning at Units 1 and 3 by April 30, 2025.
Source: POWER Magazine
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