GridStor closes $220m on a 400 MWh Arizona battery
Serguey Asael Shinder1 min readGridStor has closed a $220 million financing package for the 100 MW / 400 MWh White Tank battery project in Arizona, announced 21 September and reported by Energy-Storage.news at https://www.energy-storage.news/gridstor-closes-us220-million-financing-for-400mwh-arizona-bess/.
The package combines a tax equity bridge, construction financing and term debt, with ING Capital, KeyBank and Zions Capital Markets as the financial partners. GridStor acquired White Tank from Strata Clean Energy in September 2025; the project was originally awarded through Arizona Public Service's 2023 all-source RFP, and will run under a 20-year tolling agreement with that utility. Service is expected in the first half of the year ahead.
What it means
A twenty-year tolling agreement is what makes the other numbers financeable. Under a toll, the utility pays for the right to dispatch the battery and takes the market risk; the owner earns an availability payment. That converts a merchant asset whose revenue depends on price spreads into something close to a bond - which is the only form in which term debt and tax equity arrive together at this size.
The three-part structure is the tell about where the risk actually sits. A tax equity bridge exists because the tax benefits cannot be monetised until the asset is in service; construction financing covers the period when there is nothing to dispatch; term debt takes over once the tolling payments start. Each tranche is priced against a different risk, and the sequence is the project's own timeline written in money.
⚠️ Financing close is not commissioning. The in-service expectation is the developer's, the tolling counterparty is the utility that ran the procurement, and no price or availability terms are disclosed here.