Form Energy has opened the first commercial factory for iron-air batteries in Weirton, West Virginia, on the site of a former steelworks. Starting in 2027, the company will deliver systems that store electricity for up to 100 hours, more than 20 times longer than conventional lithium batteries. Existing contracts suggest an implicit price point around $33 per kilowatt-hour, substantially below the $80 to $100 that lithium systems command for much shorter storage durations. The missing piece in the renewable energy transition is no longer wind turbines or solar panels but storage systems that sustain supply over nights and windless days. Iron-air could fill this gap.
Why long-duration storage is the critical bottleneck
Lithium batteries store electricity efficiently for four to six hours and are economically optimized for exactly that window. When a windless period lasts three days or autumn fog covers solar panels for an extended period, short-term storage cannot help. At that point, either fossil fuel power plants must start up or electricity must be imported from abroad. This is the core problem that energy transition strategies from Germany to Australia still struggle with: how to store electricity over days without relying on geographic advantages?
Pumped-storage hydroelectricity has been the gold standard for long-duration storage. Germany operates approximately 7.5 gigawatts of installed pumped-storage capacity. The most powerful facility, the Goldisthal pumped-storage plant in Thuringia, delivers 1,060 megawatts and stores 8,480 megawatt-hours, roughly eight hours of full output. Building significantly more in central Europe is geographically constrained: pumped storage requires mountains and large bodies of water.
How iron-air works: controlled corrosion
The iron-air battery's principle relies on a process familiar from everyday experience: iron rusts. During discharge, iron oxidizes to iron oxide through contact with atmospheric oxygen, releasing electrical current. During charging, electrical current reverses the reaction, reducing iron oxide back to metallic iron. Form Energy calls this controlled corrosion. Simple as it sounds, the material advantages are substantial: iron is the fourth most abundant element in Earth's crust, globally abundant, non-flammable, and non-toxic. No rare earths like cobalt or lithium are needed.
The trade-off is efficiency. For every kilowatt-hour stored, an iron-air battery returns approximately 0.40 to 0.50 kilowatt-hours. Lithium systems achieve 85 to 90 percent efficiency. For multi-day storage, this disadvantage matters less: when surplus solar electricity is available at midday for two to three cents per kilowatt-hour, capital costs dominate the economics, not efficiency.
What Form Energy delivers and who is buying
The Weirton factory sits on the grounds of the former steelworks that closed in 2024, hitting the city hard. Form Energy projects scaling annual production to 500 megawatts of system capacity by 2028. Order volume already exceeds 75 gigawatt-hours under contract.
The largest agreements reveal where the market is heading: Crusoe Energy, which operates AI data centers and previously engaged in Bitcoin mining, ordered 12 gigawatt-hours. Xcel Energy and Google are jointly planning a data center facility in Minnesota equipped with 300 megawatts of iron-air storage and 30 gigawatt-hours of capacity. This signals that known order volume goes primarily to high-energy-demand technological infrastructure, not integration of wind parks or solar fields into public grids. Whether iron-air meaningfully contributes to power system decarbonization or initially stabilizes data centers depends on how quickly costs decline and who signs future contracts.
Comparison: Pumped storage, vanadium flow, and compressed air
Iron-air battery competition comes less from lithium systems than from other long-duration storage technologies. Vanadium redox flow batteries store electricity for four to eight hours and are considered modularly scalable. The currently largest such project, Rongke Power's facility in Dalian, China, entered operation in 2023 with 800 megawatt-hours. For 100-hour storage, such systems would cost multiples more because vanadium itself is a scarce and price-volatile metal.
Compressed air energy storage shares the geographic problem with pumped hydro: it requires underground caverns or mines. Globally, only two commercial facilities exist, including the Huntorf plant in Lower Saxony, Germany (1978, 290 megawatts), the world's first compressed air storage facility. More than four decades later it remains an exception. Iron-air requires no such geological prerequisites: factories can be built anywhere iron supply exists.
Whether iron reaches European scale by 2030 remains uncertain
Europe has preliminary plans. The European company Ore Energy announced intentions to build 50 gigawatt-hours of annual production capacity by 2030. No concrete factory location has been named. The International Energy Agency estimates that decarbonizing Europe's electricity market by 2035 requires up to 100 gigawatts of additional long-duration storage capacity, of which a tiny fraction is currently planned.
For the global renewable energy transition, Form Energy's factory represents proof that the technology works at scale, not just in laboratories. Whether iron-air becomes an industry standard for energy transition infrastructure or remains a niche solution for technology companies will be answered by the market in the next two years.