A Battery That Runs on Rust Just Raised $750 Million

Form Energy has raised $750 million to build more of its iron-air batteries at a factory in West Virginia. The company has now raised over $2 billion in total (TechCrunch; WSJ).

The round was led by T. Rowe Price, with participation from Sequoia Capital, Janus Henderson, Franklin Templeton, PEAK6 Investments, Prelude Ventures, Engine Ventures, TPG Rise Climate, Capricorn's Technology Impact Funds, Breakthrough Energy Ventures, Dustin Moskovitz and Cari Tuna, Gigascale Capital, Coatue, Energy Impact Partners, NGP, GE Vernova, Blindspot Ventures, and M&G Catalyst Fund (TechCrunch).

Form Energy makes a battery that can deliver power for up to 100 hours. That is much longer than the lithium-ion batteries most people know from phones and electric cars, which typically run for a few hours. Instead of lithium, the battery uses iron. When the battery produces power, the iron turns to rust. When the battery charges back up, the rust turns back into iron. The company says about 80% of its materials come from the U.S., with the rest from Europe and Asia, and none from China (TechCrunch).

The company has a growing list of customers. Form Energy reports orders for about 80 gigawatt-hours of batteries, four times more than earlier in 2026. Google is building a data center in Minnesota that will partly run on a Form Energy battery costing about $1 billion. Crusoe, another data center company, said in March 2026 it would buy 12 gigawatt-hours of Form Energy batteries. Utility companies Xcel Energy and FuturEnergy Ireland have also signed on, with the Irish project being the first of its kind in that country (TechCrunch).

The bigger picture matters here. U.S. data centers are expected to use four times as much electricity by 2035, reaching about 20% of all power generated in the country. In the first three months of 2026, the U.S. installed 9.7 gigawatt-hours of energy storage, up 32% from the same period a year earlier (TechCrunch).

This latest round of funding follows earlier ones. Form Energy raised $405 million in October 2024 and $450 million in 2022, which included investment from the steel company ArcelorMittal (Form Energy; Energy Storage News). The U.S. Department of Energy awarded the company $150 million in September 2024 to help build the West Virginia factory (Form Energy). Factory expansion began in October 2024.

The mix of investors in this round is worth noting. Alongside firms focused on climate technology, the round includes major financial companies like T. Rowe Price, Franklin Templeton, and Coatue, plus GE Vernova, a power equipment company. That combination suggests iron-air batteries are being judged as a practical business, not just a promising science experiment. The cost of building and financing these batteries, and whether customers follow through on their orders, now matter more than whether the technology works.

The data center demand tells its own story. Most batteries installed today can only deliver power for two to four hours. A battery that runs for 100 hours solves a different problem: keeping the lights on when wind and solar aren't producing for days at a time, or covering periods when electricity prices spike. The fact that Google and Crusoe are buying these batteries suggests large tech companies see multi-day storage as a separate need, not just a bigger version of the batteries they already use.

The supply chain advantage is real but unproven at scale. Because 80% of Form Energy's materials come from the U.S. and none from China, the company avoids the tariffs and political tensions that affect lithium-ion supply chains. Whether that translates into lower costs at large scale depends on how efficiently the West Virginia factory can produce batteries.

The $750 million will go toward expanding that factory. The company has not shared specific timelines or plans for additional factories. The orders, the customers, and the money are all in place. The question now is whether Form Energy can build fast enough to meet them.