GridStor wins financing for 400 MWh BESS in Arizona, tolling secured with state utility

A large battery storage project is moving forward in Arizona, backed by $220 million in financing. GridStor, a developer backed by Goldman Sachs, is building the White Tank battery energy storage system in Maricopa County, near Phoenix. The facility will store 400 megawatt-hours of electricity and is set to start operating in the first half of 2027. It will run under a 20-year agreement with Arizona Public Service (APS), the local utility, which will use the stored power to help balance supply and demand on its grid.

This matters to Arizona homeowners because APS has been setting new records for peak power demand, driven by population growth, new manufacturing (including computer chip plants), and data centers. That rising demand puts pressure on the grid, especially during hot summer days when air conditioning use spikes. Battery storage projects like White Tank are designed to store power when it's plentiful and release it when demand surges, which can help prevent strain on the system and support more reliable service.

The project is being financed by three banks — ING Capital, KeyBank, and Zions — through a mix of loans and other financial tools. It's the fourth financing deal GridStor has completed in the past year as the company expands its battery storage holdings across the country. For homeowners, this kind of investment in grid infrastructure is generally a sign that utilities are working to keep pace with growing electricity demand in fast-growing areas like the Phoenix region.