The Salt River Project (SRP) Board of Directors has approved development of the 1.7 GW Marigold Energy Center in Stanfield, Arizona, combining solar generation, battery storage and natural gas-fired capacity with new transmission infrastructure.
The project will comprise 600 MW of solar generation, 400 MW of eight-hour battery storage and 675 MW of natural gas generation. SRP said the combination is intended to provide dispatchable capacity as electricity demand increases across Maricopa and Pinal counties, while supporting the integration of additional renewable generation.
The site will also include a 230 kV/500 kV substation and approximately four miles of new 230 kV transmission lines. The additional network infrastructure is intended to increase the flexibility of the local grid and connect the new generation and storage resources to the wider system.
Construction is scheduled to begin in January 2027, with commercial operation targeted for 2032.
Marigold forms part of SRP’s plan to more than double its power system capacity by 2035. The utility is pursuing a combination of natural gas, renewable generation and energy storage as it expands the system.
The project is also being developed within SRP’s sustainability targets for reducing carbon emissions and water consumption. The utility has not provided a specific emissions profile for the completed facility.
Regional public power utility Electrical District No. 3 is assessing a potential agreement to procure part of the Marigold output for customers in Maricopa, Stanfield and surrounding areas.
The project still requires regulatory approval for its natural gas generation and transmission infrastructure. SRP has applied to the Arizona Corporation Commission for a Certificate of Environmental Compatibility. A Power Plant and Transmission Line Siting Committee hearing is scheduled for 21–25 September, with an ACC decision expected in November 2026.
The combination of long-duration storage and gas generation reflects the system requirement for capacity that can complement variable renewable output and respond to demand throughout the day and night.
