GridStor closes US$220 million financing for 400MWh Arizona BESS
GridStor, a US-based developer and operator of grid-scale battery energy storage systems (BESS), has closed a US$220 million financing agreement for the 100MW/400MWh White Tank project in Arizona, US.
Announced 21 September, GridStor closed the US$220 million tax equity bridge, construction, and term debt financing agreement with financial partners ING Capital LLC, KeyBank N.A., and Zions Capital Markets, to complete development of the 400MWh White Tank BESS project.
In September 2025, GridStor acquired White Tank from Strata Clean Energy, which was originally awarded the project through utility Arizona Public Service’s (APS) 2023 all-source request for proposals (RFP).
White Tank will be operated via a 20-year tolling agreement with APS. It is expected to be placed in service in the first half of 2027.
GridStor stated that its construction of standalone BESS in Arizona comes as the state’s utilities break all-time records for power demand, with APS notching peak electricity service on 2 August that was 5% higher than the previous record set in 2025.
The White Tank battery storage project will reinforce APS’ system reliability, helping to ensure electric customers have access to power and sustain the region’s expanding population and new industrial facilities.
In August, utility Tucson Electric Power (TEP) completed the expansion of its Roadrunner Reserve BESS in southeast Tucson, bringing the total capacity to 400MW/1,600MWh.
The month prior, IPP Enlight Renewable Energy announced that its US subsidiary Clēnera Holdings entered into a debt financing framework agreement for the CO Bar Complex in Arizona, which consists of five projects with a combined capacity of approximately 1.2GW of solar PV generation and 4GWh of BESS.
Also in June, carbon dioxide-based long-duration energy storage (LDES) company Energy Dome and Arizona public utility Salt River Project (SRP) announced a 19MW/190MWh CO2 Battery project in St. Johns.
In May, GridStor acquired the 199MW/796MWh Birdseye BESS project in Adams County, Colorado, from renewables developer Accelergen. That project marked the company’s fifth acquisition in 18 months.