On 2025‑10‑10, ESS Tech (NYSE: GWH) announced a new 50 MWh long‑duration energy storage pilot project with Salt River Project (SRP), a not‑for‑profit public power utility serving the Phoenix metropolitan area. The agreement adds a 5 MW, 50 MWh battery system—built on ESS’s Energy Base iron‑flow platform—to SRP’s Copper Crossing Energy and Research Center in Florence, Arizona, and will sell capacity to SRP under a ten‑year energy storage agreement.
The 50 MWh system will store enough energy to power 1,125 average‑size homes for 10 hours, demonstrating the practical capability of ESS’s iron‑flow technology to deliver extended‑duration storage at scale. By deploying the Energy Base platform in a real‑world utility setting, ESS gains a high‑profile validation that can accelerate adoption among other utilities and large commercial customers seeking non‑lithium, long‑duration solutions.
This customer win is material for ESS because it confirms demand for its core product, expands its footprint in the U.S. utility market, and provides a tangible case study that can be leveraged in future sales efforts. The project also aligns with SRP’s goal to evaluate emerging, non‑lithium LDES technologies, positioning ESS as a key partner in the broader transition to sustainable, long‑duration energy storage.
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