Arizona's Record-Breaking Power Demand Drives $220 Million Financing for GridStor's Maricopa County Battery Project

Portland-based battery storage developer GridStor has secured a USD 220 million debt financing package to fund the construction of a 100 MW facility in Maricopa County, Arizona — a deal that lenders say reflects the energy storage sector's emergence as a cornerstone of modern grid infrastructure.

A Facility Built Around Surging Arizona Demand

The White Tank battery energy storage project, located in Maricopa County, is designed to deliver 100 MW of power capacity backed by 400 MWh of energy storage. The impetus for the project is tied directly to accelerating electricity consumption in the state. GridStor noted that Arizona Public Service set an all-time peak electricity record on August 2 of this year, a level 5 percent higher than the previous record set in 2025.

The White Tank facility is intended to reinforce system reliability for APS customers amid a rapidly expanding population and a growing base of industrial facilities. Once operational, the facility will run under a 20-year tolling agreement with Arizona Public Service, the largest electric utility in the state, serving approximately 1.4 million homes and businesses. GridStor expects the facility to be placed in service in the first half of 2027.

How the USD 220 Million Package Was Structured

The financing was arranged with three lenders: ING Capital LLC, KeyBank N.A., and Zions Capital Markets. The package combines a tax equity bridge loan with construction and term debt, a structure commonly used in large-scale energy infrastructure transactions to bridge the gap between project completion and the receipt of tax equity proceeds. KeyBanc Capital Markets served as arranger for the financing. Each of the three institutions brought perspectives on why the transaction made sense for their respective organizations.

Filipe Barreto, Director at ING, said the deal reflects ING's view that battery energy storage assets have become an integral part of energy infrastructure and represent one of the primary themes in energy financing.

He cited rapid growth in renewable generation as a key driver of demand for storage solutions and described the deal as consistent with ING's commitment to financing infrastructure that enhances grid reliability and supports a lower-carbon energy future. Greg Berman, Managing Director for Utilities, Power, and Renewable Energy at KeyBanc Capital Markets, characterized battery storage as an essential part of how utilities are addressing growing load and reliability requirements.

He described the asset class as one that can be deployed quickly and at scale to meet evolving energy needs across the country. Robert Park, Head of Power and Project Finance at Zions Capital Markets, said the transaction demonstrates his team's expertise in structuring tailored financial solutions in the power sector and described it as strategic financing that supports the continued growth of Arizona's energy capacity.

GridStor's Pipeline and Financial Backing

The White Tank deal marks GridStor's fourth major financing milestone in the past twelve months. The company, headquartered in Portland, Oregon, develops and operates utility-scale battery energy storage systems and manages a project pipeline of more than 3 gigawatts of battery storage projects in later-stage development or under construction across the western and central United States.

GridStor is backed by Goldman Sachs Asset Management. Chris Taylor, CEO of GridStor, said trusted financial partnerships are critical for advancing large-scale power supply and infrastructure to meet surging demand for new power capacity.

The company said it expects to continue acquiring advanced-stage projects that provide cost-effective, near-term solutions to utilities, data centers, and other large industrial customers in regions with rapidly growing energy demand.

About the Institutions Behind the Deal

ING Capital LLC is an indirect U.S. subsidiary of ING Bank NV, itself part of ING Groep NV, a global financial institution with more than 60,000 employees offering retail and wholesale banking services to customers in over 100 countries. ING Capital provides wholesale financial lending products and advisory services to corporate and institutional clients.

KeyBanc Capital Markets operates as the corporate and investment banking division of KeyCorp, a Cleveland, Ohio-headquartered institution that traces its origins more than 200 years to Albany, New York. As of June 30, 2026, KeyCorp reported approximately USD 191 billion in assets and operates approximately 950 branches and 1,100 ATMs across 15 states under the KeyBank National Association name.

Its capital markets arm provides products including merger and acquisition advice, public and private debt and equity, syndications, and derivatives to middle market companies across selected industries. Zions Capital Markets serves as the capital markets arm of Zions Bancorporation, with Robert Park's Power and Project Finance team having structured the White Tank financing package.