Form Energy is developing iron-air batteries capable of storing electricity for 100 hours or more — a duration category that lithium-ion cannot address economically. The company was founded in 2017 in Berkeley, California by Mateo Jaramillo (former VP of Energy Products at Tesla), Yet-Ming Chiang (MIT materials science professor and serial battery entrepreneur), Marco Ferrara, and Ted Wiley. It is now headquartered in Pittsburgh, Pennsylvania, with manufacturing operations in Weirton, West Virginia.
The company's founding premise is that the clean energy transition has a multi-day storage problem. Lithium-ion batteries are well-suited to short-duration applications — four hours of discharge at peak pricing, frequency regulation, backup power — but their cost makes them uneconomical for storage durations measured in days. Weather events like extended cloud cover, wind lulls, and seasonal demand shifts can create multi-day gaps in renewable generation that no amount of four-hour batteries can bridge. Form Energy's iron-air technology is designed specifically to fill that gap, at a cost target that makes it economically viable as a grid resource rather than a niche backup product.
Iron-air batteries operate on the electrochemical equivalent of rusting and de-rusting iron. During discharge, iron pellets inside the battery cells are exposed to oxygen drawn from the surrounding air, causing them to oxidize — the same process as rust forming on exposed metal. This oxidation reaction releases electrons, generating electrical current. During charging, an electrical current reverses the process, stripping oxygen away from the iron oxide and reducing the iron back to its metallic state, ready for another discharge cycle.
The appeal of this chemistry is its use of iron — one of the most abundant, cheap, and non-toxic materials on earth — as the primary energy storage medium. Iron is roughly $0.10 per kilogram. Lithium and cobalt, by contrast, are geographically concentrated, supply-constrained, and significantly more expensive. Form Energy's cost target of approximately $20 per kilowatt-hour at scale is achievable in large part because the active material is cheap steel, not refined lithium compounds. The manufacturing facility in Weirton, West Virginia — built in a region with a century of iron and steel production heritage — is designed to produce batteries at the scale and cost required for utility deployment.
The primary trade-off is round-trip efficiency. Iron-air batteries are estimated at approximately 30–50% round-trip efficiency, substantially lower than lithium-ion's ~85–95%. For a short-duration application, that efficiency gap is prohibitive. For a long-duration application where the alternative is curtailing renewable generation or keeping gas peakers on standby, the economics can still favor iron-air — the value is in the low capital cost per unit of energy stored, not in cycle efficiency.
Form Energy's first commercial deployment is a 15 MW / 1,500 MWh system contracted with Georgia Power, a subsidiary of Southern Company. At 100 hours of rated duration, this represents the first iron-air system at commercial scale. The project will demonstrate the technology's performance under real grid conditions and provide operational data to support future utility procurement decisions. Southern Company's engagement is significant — it is one of the most conservative and regulated of the major U.S. utilities, and its willingness to pilot iron-air storage reflects growing utility interest in long-duration options beyond pumped hydro.
Form Energy's manufacturing facility in Weirton, West Virginia occupies a former steel mill site and is designed to produce iron-air batteries at gigawatt-hour scale. The choice of Weirton is strategic on multiple dimensions: the region's manufacturing infrastructure and workforce are suited to the kind of high-volume, materials-intensive production required; the Department of Energy and state of West Virginia have provided support; and the location in a historically coal-dependent region provides a political narrative around energy transition job creation that has resonated with federal policymakers.
Form Energy's near-term priority is proving out the iron-air technology at commercial scale and demonstrating the reliability and cost profile that utility procurement teams require. The Georgia Power deployment is the critical proving ground. If the system performs as modeled, it substantially de-risks the technology for subsequent buyers and enables Form Energy to move from pilot deployments to utility-scale contracting.
The longer-term strategic bet is that grid operators and utilities will increasingly need multi-day storage as renewable penetration rises above 60–70% of the generation mix. At those penetration levels, the multi-day weather correlation problem becomes acute — a regional weather event can simultaneously suppress wind and solar generation across an entire grid for days at a time. No amount of short-duration storage addresses that. Pumped hydro, the only established multi-day storage technology, is site-constrained and takes a decade to permit and build. Iron-air is designed to fill that gap with a technology that can be manufactured at scale, sited almost anywhere, and deployed in 12–18 months.
ArcelorMittal's participation as a Series E lead investor is strategically important beyond the capital: the world's largest steel company has a direct commercial interest in iron-air batteries succeeding, both as a buyer of iron raw material and as a potential manufacturing partner. The relationship provides Form Energy with access to global steel supply chains and potential co-manufacturing arrangements that could accelerate cost reduction.
Iron-air batteries have never been deployed at utility scale before. The performance characteristics modeled in laboratory and pilot conditions — round-trip efficiency, cycle life, degradation rate, maintenance requirements — need to be validated at commercial scale over multi-year periods. Utilities procuring long-duration storage will require several years of operational data before committing to large deployments, which creates a long adoption timeline even if the Georgia Power pilot performs as expected.
The low round-trip efficiency (~30–50%) is a genuine technical constraint. In markets where electricity prices are volatile and arbitrage value is high, efficiency matters significantly. Iron-air is best suited to applications where the value of having energy available — capacity value, avoiding curtailment — outweighs the efficiency penalty. As renewable penetration grows, those conditions become more common, but the economic case varies meaningfully by market.
Competing long-duration storage technologies — flow batteries (vanadium, iron-chromium), compressed air, gravity storage, green hydrogen — are all pursuing the same market opportunity with different technical approaches and cost trajectories. Form Energy has the most advanced iron-air program globally, but the long-duration storage market is early enough that no single technology has established dominance.
This profile was compiled from publicly available information including:
Form Energy Newsroom — Product announcements, partnership disclosures, and manufacturing updates.
Form Energy Series E funding announcement (2022); Georgia Power pilot project announcement; Weirton manufacturing facility announcement.
U.S. Department of Energy Advanced Manufacturing Office; West Virginia Economic Development Authority.
This profile is for informational purposes only and does not constitute investment advice, a recommendation, or a solicitation to buy or sell any security. Form Energy is a private company; financial data is limited to publicly disclosed information.