GridStor secured $220 million in tax equity bridge, construction, and term debt from ING Capital, KeyBank, and Zions Capital Markets to finish its 100 MW/400 MWh White Tank battery storage project in Arizona, which will operate under a 20 year tolling deal with APS starting in the first half of 2027.
GridStor closed a $220 million tax equity bridge, construction, and term debt financing package for its 100 MW / 400 MWh White Tank battery energy storage system (BESS) in Maricopa County, Arizona.
The financing, provided by ING Capital LLC, KeyBank N.A. (via KeyBanc Capital Markets), and Zions Capital Markets, supports completion of the project, which is expected to enter commercial operation in the first half of 2027. It operates under a 20 year tolling agreement with Arizona Public Service (APS), the state’s largest electric utility, serving roughly 1.4 million homes and businesses. Under the tolling structure, APS controls charging and discharging to support system reliability.
White Tank is a standalone four hour duration facility sited near Avondale, adjacent to APS’s Colter substation. GridStor acquired the project from Strata Clean Energy in September 2025. Strata had originally secured it through APS’s 2023 all source request for proposals and arranged the long term tolling agreement; Strata retained a consultative role through commercial operations. Battery supply includes approximately 120 SolBank 3.0 enclosures from e-STORAGE (Canadian Solar).
The financing enables construction to advance, with the project positioned to add flexible capacity amid Arizona’s surging electricity demand. APS set multiple peak records in summer 2026, including 9,164 MW on August 2 (about 5% above the prior 2025 record), driven by extreme heat, population growth, and industrial expansion, particularly data centers, which accounted for a substantial share of recent peak growth. Arizona utilities project significant further increases in peak load over the coming decade.
What is GridStor?
GridStor, founded in 2022 and headquartered in Portland, Oregon (with offices in Denver and Los Angeles), develops, acquires, builds, and operates utility scale standalone BESS primarily across the western and central United States. It is backed by the Sustainability and Infrastructure Investing groups of Goldman Sachs Asset Management. The company currently reports more than 3 GW of projects in later stage development or under construction, with approximately 280 MW / 600 MWh in operation and 250 MW / 700 MWh under construction. Leadership brings extensive experience from large scale power generation and storage development.
This $220 million close represents GridStor’s fourth major financing milestone in the prior 12 months. Recent activity includes a $120 million package (March 2026) with NORD/LB and Siemens Financial Services for the 150 MW / 300 MWh Gunnar project in Hidalgo County, Texas, and the acquisition of the 199 MW / 796 MWh Birdseye project in Colorado (May 2026). The company emphasizes acquiring advanced stage, contracted projects that can deliver near term reliability solutions to utilities, data centers, and large industrial customers in high growth load areas.
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The multi tranche package combines a tax equity bridge (facilitating monetization of available tax incentives), construction debt, and longer term debt. This structure is typical for contracted BESS assets and reflects lenders’ increasing view of battery storage as core energy infrastructure rather than a speculative technology. Comments from the financing partners highlighted the role of BESS in addressing renewable growth, rising load, and reliability needs, with ING describing storage assets as “one of the primary themes in energy financing.”
The long term APS tolling agreement provides contracted revenue visibility through the mid 2040s, reducing merchant risk and supporting debt sizing. GridStor’s Goldman Sachs backing and track record of project acquisitions and financings position it to continue scaling in markets facing rapid demand growth and grid constraints.
The transaction advances GridStor’s portfolio in a high demand desert Southwest market where utilities are adding storage to manage evening peaks, support renewable integration, and accommodate industrial and data center load. It underscores the maturation of project finance for utility scale BESS, with established banks providing substantial capital against contracted offtake. For Arizona, White Tank contributes flexible capacity that can help maintain reliability as peak demand continues to climb and the resource mix evolves. GridStor intends to pursue further acquisitions of similar advanced stage projects that offer cost effective, near term solutions in regions with rapidly growing energy needs.
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