GridStor, a developer and operator of utility-scale battery energy storage systems (BESS), has closed a $220 million tax equity bridge, construction, and term debt financing agreement to complete its 100 megawatt (MW)/400 megawatt-hour (MWh) White Tank battery storage facility in Maricopa County, Arizona.
ING Capital, KeyBank, and Zions Capital Markets served as financial partners on the transaction.
The White Tank facility will operate under a 20-year tolling agreement with Arizona Public Service (APS), the state’s largest electric utility serving approximately 1.4 million homes and businesses, and is expected to be placed in service in the first half of 2027.
The project comes as Arizona utilities are setting new power demand records, with APS recording its highest-ever peak electricity service on August 2 — 5% above the previous record set in 2025.
“Trusted partnerships like these are critical for advancing large-scale power supply and infrastructure to meet surging demand for new power capacity. We thank ING, KeyBanc Capital Markets, and Zions for placing their trust in us,” said Chris Taylor, CEO of GridStor, in a statement.
The financing marks GridStor’s fourth major financial milestone in the past twelve months. Backed by Goldman Sachs Asset Management, the company manages a pipeline of more than 3 gigawatts (GW) of battery storage projects in later-stage development or under construction across the western and central United States.
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