Form Energy

Overview

Form Energy is developing iron-air batteries that store electricity for 100 hours or more, a duration category lithium-ion cannot address economically. It was founded in 2017 by Mateo Jaramillo, former VP of Energy Products at Tesla, Yet-Ming Chiang, an MIT materials science professor and serial battery entrepreneur, Marco Ferrara, and Ted Wiley. The company is headquartered in Somerville, Massachusetts, with an engineering office in Berkeley and manufacturing in Weirton, West Virginia. Form began commercial battery production at Weirton in 2025 and has since signed its largest deal, a 300 MW / 30 GWh iron-air system to help power a Google data center in Minnesota.

The founding premise is that the clean energy transition has a multi-day storage problem. Lithium-ion suits short-duration work: four hours of discharge at peak pricing, frequency regulation, backup power. Its cost makes it uneconomical for storage measured in days. Extended cloud cover, wind lulls, and seasonal demand shifts create multi-day gaps in renewable generation that no quantity of four-hour batteries can bridge. Iron-air is designed to fill that gap at a cost that makes it a grid resource rather than a niche backup product.

Iron-air chemistry

Iron-air batteries run on the electrochemical equivalent of rusting and un-rusting iron. During discharge, iron pellets inside the cells are exposed to oxygen drawn from the surrounding air and oxidize, the same process as rust forming on exposed metal, and the reaction releases electrons that generate current. During charging, an electrical current reverses it, stripping oxygen from the iron oxide and reducing the iron back to metal, ready for another cycle.

The appeal is the material: iron is among the most abundant, cheap, and non-toxic substances on earth, at roughly $0.10 per kilogram. Lithium and cobalt are geographically concentrated, supply-constrained, and far more expensive. Form's cost target of approximately $20 per kilowatt-hour at scale is reachable largely because the active material is cheap steel rather than refined lithium compounds. The Weirton plant, built in a region with a century of iron and steel production behind it, is designed to produce batteries at the scale and cost utility deployment requires.

The trade-off is round-trip efficiency. Iron-air is estimated at roughly 40% to 50%, an estimate rather than an audited field figure, against lithium-ion's 85% to 95%. For short-duration work that gap is prohibitive. For long-duration work where the alternative is curtailing renewable generation or holding gas peakers on standby, the economics can still favor iron-air, because the value sits in low capital cost per unit of energy stored rather than in cycle efficiency.

Deployments & partnerships

Strategy & outlook

The near-term priority is proving iron-air at commercial scale and demonstrating the reliability and cost profile utility procurement teams require. The Great River Energy deployment, the first system on the grid, is the critical test. If it performs as modeled, it substantially de-risks the technology for later buyers and lets Form move from pilots to utility-scale contracting.

The longer-term bet is that grid operators will need multi-day storage as renewable penetration passes 60% to 70% of the generation mix. At those levels the multi-day weather correlation problem turns acute: a regional weather event can suppress wind and solar across an entire grid for days. No quantity of short-duration storage answers that. Pumped hydro, the only established multi-day technology, is site-constrained and takes a decade to permit and build. Iron-air is designed to fill the gap with something manufacturable at scale, sitable almost anywhere, and deployable in 12 to 18 months. The Google and Xcel deal points to a second demand driver: firm, around-the-clock capacity for the fast-growing load of AI data centers.

Form's strategic investors matter beyond the capital. ArcelorMittal, one of the world's largest steel companies and a Series E investor, has a direct commercial interest in iron-air succeeding, both as a supplier of iron and as a potential manufacturing partner, which opens global steel supply chains. GE Vernova, which joined the 2024 Series F, brings grid-equipment and power-systems reach that can carry iron-air into utility procurement at scale.

Key considerations

Iron-air batteries have never been deployed at utility scale. Performance modeled in laboratory and pilot conditions, including round-trip efficiency, cycle life, degradation rate, and maintenance requirements, has to hold at commercial scale over multi-year periods. Utilities procuring long-duration storage will want several years of operational data before committing to large deployments, which makes for a long adoption timeline even if the first pilots perform as expected.

The low round-trip efficiency is a genuine technical constraint. In markets with volatile electricity prices and high arbitrage value, efficiency matters a great deal. Iron-air suits applications where the value of having energy available, whether capacity value or avoided curtailment, outweighs the efficiency penalty. Those conditions grow more common as renewable penetration rises, and the economic case still varies substantially by market.

Competing long-duration technologies are chasing the same opportunity from different directions: flow batteries with vanadium and iron-chromium chemistries, nickel-hydrogen, zinc-based cells, thermal storage at Antora Energy, compressed air, gravity storage, and green hydrogen. Form has the most advanced iron-air program anywhere, and the long-duration market is early enough that no technology has established dominance.

Policy cuts both ways. The 2025 One Big Beautiful Bill Act spared standalone storage the accelerated phase-out it imposed on wind and solar, keeping the 48E investment tax credit on a longer runway, and Form's U.S.-made iron and domestic manufacturing sit well against foreign-entity and domestic-content rules. Against that, the same law's cuts to wind and solar credits could slow the renewable buildout that drives long-duration storage demand, and federal support is not assured: a Form-linked Department of Energy award tied to the Xcel projects was among grants canceled in October 2025, though the Weirton factory award was reportedly retained.

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