ESS Tech, Inc.

ESS Tech, Inc.

ESS Tech, Inc. was founded in 2011 in Wilsonville, Oregon, by a team of engineers aiming to commercialize iron-flow battery technology for stationary energy storage. The company went public in October 2021 through a merger with a SPAC, ACON S2 Acquisition Corp., raising approximately $380 million (per SEC filings, 2021). The firm's core product is the Energy Warehouse, a modular iron-flow battery designed for 4–12 hour duration applications, targeting utilities, independent power producers, and commercial-industrial customers. Unlike lithium-ion systems, ESS Tech's batteries use iron, salt, and water as electrolytes, which the company claims reduces fire risk and mineral-sourcing concerns (per the firm's SEC filings, 2023). Deployment is primarily in North America, with pilot projects in Europe and Australia; key customers include Pacific Gas & Electric and Southern Company (per company press releases, 2022–2024). The company also partners with SB Energy, a renewable energy developer, for multi-hundred-megawatt installations. As of early 2025, ESS Tech employed approximately 280 people, per public filings, with operations centered in Oregon. The company reported a net loss of $73.6 million on $8.3 million in revenue for fiscal 2024 (per SEC filings). It received a $50 million grant from the U.S. Department of Energy's Office of Manufacturing and Energy Supply Chains in 2023 to scale domestic manufacturing (per DOE, September 2023). ESS Tech's structural differentiator is its focus on a single technology — iron-flow batteries — for long-duration storage, a niche that avoids competition with lithium-ion for shorter cycles. The firm's public listing provides capital access but subjects it to quarterly earnings scrutiny; its ability to scale production while reducing costs will determine whether iron-flow chemistry becomes a meaningful part of the grid storage mix.