The Arizona Corporation Commission has unanimously approved the conversion of the Springerville and Coronado coal-fired power plants to natural gas. The decision was made during an open meeting on March 4, 2026.
Springerville Generating Station is owned and operated by Tucson Electric Power (TEP), while Salt River Project (SRP) owns and operates the Coronado Generating Station. Both facilities have faced uncertainty due to federal mandates that would require their closure within six years.
Commissioner Kevin Thompson stated, “The conversion of these plants will result in a dramatic reduction in emissions, an increase in the performance and efficiency of the plants, increase the lifespan of the plants, preserve quality jobs, maintain significant revenues for local communities, and is the most cost-effective way to maintain grid reliability. These plants are cornerstones of their local communities, and once converted to natural gas, will become a key pillar of long-term grid reliability versus being seasonally operated generating stations. I’m pleased to see that the utilities are listening to this Commission and have opted to put forward solutions that will put the best interests of ratepayers and the grid ahead of disastrous political objectives.”
TEP owns two out of four units at Springerville but manages operations for all units under contract with other owners. The company requested approval to convert Units 1 and 2 from coal-fired boilers to natural gas-fired boilers. TEP expects construction on a new natural gas pipeline serving Springerville to finish by late 2029, with conversion work on Units 1 and 2 completed by early 2030.
Currently, Springerville Units 1 and 2 provide between 700-800 megawatts (MW) of base load electricity. To comply with EPA regulations while continuing coal operations past mandated closure dates would require more than $450 million in upgrades—costs that would be passed on to customers. By contrast, converting these units to natural gas is estimated at $170 million.
For Coronado Generating Station, SRP plans for necessary infrastructure upgrades and unit conversions also by late 2029. The total cost for Coronado’s conversion through 2045 is projected at $1.1 billion—including both conversion expenses and ongoing operations. Building a new natural gas plant instead would cost approximately $300 million more over the same period. SRP evaluated using long-duration lithium-ion batteries as an alternative; however, this option would add about $1.2 billion in costs compared with conversion while reducing available firm capacity.
Coronado currently provides around ten percent of SRP’s peak demand—enough electricity for more than 150,000 homes—and is considered essential for maintaining reliable service for customers.
For further information, Commissioner Kevin Thompson can be reached at Thompson-Web@azcc.gov.
