Arizona's big utility booked a four-hour battery for twenty years - and the banks closed $220 million behind it
Goldman-backed GridStor closed $220 million for its White Tank 100 MW / 400 MWh battery in Maricopa County. Arizona Public Service holds a 20-year toll. In-service target: first half of 2027.
Picture a desert city that keeps setting new peak demand records because people, chip plants, and data halls all want power at once. A utility can build more generation - or it can book a battery that soaks cheap hours and pours them back when the afternoon spike hits.
ESS News reports GridStor, backed by Goldman Sachs, secured financing for the White Tank battery energy storage system in Arizona. On the page: 100 MW / 400 MWh - four hours at full power - with a 20-year tolling agreement with Arizona Public Service (APS). Three banks (ING Capital, KeyBank, and Zions Capital Markets) structured a $220 million package across tax-equity bridge, construction, and term debt. GridStor calls it its fourth financing move in twelve months. The project sits in Maricopa County, where most of Phoenix sits, and is expected in service in the first half of 2027.
A toll here means APS pays for the right to use the battery's capacity under contract terms, while the developer owns and finances the kit. It is closer to leasing a warehouse fridge for twenty summers than buying every panel on the roof yourself.
APS demand context on the same page: an August 2026 peak that ran about 5% above the 2025 record, with growth tagged to population, manufacturing (including chip fabs), and data centres. The battery is framed as a reliability tool for that demand spike - not as a residential rebate.
Good: a named state utility offtaker, a published MW/MWh size, a twenty-year term, and a dollar figure on the financing close. That is how procurement reads a storage deal - who pays, for how long, and what box lands.
Bad: this is a utility-scale Arizona project, not your shed battery or an Australian state voucher. The $220 million is the project finance stack. It is not a price list for your site. ESS News does not publish APS's internal cost of energy or your bill impact.
Ugly: tolling still leaves operating risk, interconnection, and market rules with the people who run the box. We will not invent a payback year or a cents-per-kWh saving for a warehouse from this close.
Soft next step: if your board is asking whether a long offtake or a self-owned box fits a rising daytime-evening spike, map the site's power shape first - then talk to Sovryn Energy at /consult about the contract shape, not the headline megawatts.
Source: ESS News, 22 Sep 2026 - GridStor wins financing for 400 MWh BESS in Arizona, tolling secured with state utility. Restated published MW/MWh, $220m finance package, 20-year APS toll, and in-service window. No site payback on this page.