ESS Tech, Inc.
ESS Tech, Inc. (NYSE: ESS) is a long-duration energy storage company specializing in iron flow battery technology. The company designs and produces batteries predominantly using earth-abundant materials including salt, iron, and water that are engineered to cycle over 20,000 times without capacity fade. ESS operates… From the company’s description.
Margins and return on equity change in ; everything else in percent. Fewer shares and less debt are shown plainly, not as bad news — it depends what you make of buybacks. Dotted labels explain each measure. is shown separately from the annual figures.
What ESS Tech, Inc. does
In the company’s own words
ESS Tech, Inc. (NYSE: ESS) is a long-duration energy storage company specializing in iron flow battery technology. The company designs and produces batteries predominantly using earth-abundant materials including salt, iron, and water that are engineered to cycle over 20,000 times without capacity fade. ESS operates through its core technology platform, which includes battery stacks, electrolyte management solutions, and proprietary power trains that can be configured into complete storage solutions for various applications.
The company's primary product offering is the Energy Base, a gigawatt-hour scale, fully configurable energy storage system designed for deployment at customer sites. ESS also continues to provide warranty and maintenance services for earlier-generation products, the Energy Warehouse and Energy Center. The core intellectual property and competitive differentiation reside in proprietary components including the Proton Pump, which solves the hydroxide buildup problem that plagued earlier iron flow battery designs, along with the power module, Battery Management System, and electrolyte formulation.
ESS serves utilities, Independent Power Providers, and commercial and industrial end users in both behind-the-meter and front-of-the-meter applications. Behind-the-meter customers include data centers, microgrids, and critical infrastructure assets seeking energy cost reduction and renewable integration. Front-of-the-meter customers are primarily utilities and IPPs requiring grid-scale storage for renewable energy balancing and grid reliability.
The company was founded in 2011 and became publicly traded through a business combination with ACON S2 Acquisition Corp. in 2021. As of December 31, 2025, ESS employed 62 full-time employees based primarily at its headquarters in Wilsonville, Oregon. The company has invested approximately $184.7 million in research and development since January 2019 and maintains a patent portfolio exceeding 315 granted, applied for, or pipeline patents. ESS's website is located at https://investors.essinc.com/. The company's iron flow battery technology addresses long-duration energy storage applications where it expects to achieve lower levelized cost of storage compared to lithium-ion alternatives for storage durations exceeding eight hours.
Company details
- Sector
- Technology
- Industry
- Electronic Equipment
- Headquarters
- WILSONVILLE, OR
- Fiscal year end
- December
- CIK
- 1819438
- SIC
- 3690
Financial performance, year by year
Fiscal 2021–2025 · USDThe full income statement, balance sheet and cash flow for each of these years — every figure traceable to its filing — is on the Financials tab with a free account.
Who owns ESS Tech, Inc. — and what changed
Funds as of 2026Q2 · superinvestors as of 2026-06-30
Largest fund holders · ESS Tech, Inc.’s weight in each
Fund ownership is a floor, not a census — pensions, insurers and people holding shares directly are not visible here.
Fund ownership counts N-PORT filers only, so it is a floor rather than a census — pensions, insurers and direct holders are not visible here, and the remainder is not “held by individuals”.
Could not be determined for this company: bond issues.
Every fund and institutional holder, quarter by quarter, is on the Ownership tab with a free account.
Recent filings
All filings →Each filing opens into its own statements and disclosures here.
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