Form Energy, the Somerville-based startup building batteries that store electricity for up to 100 hours by rusting and de-rusting iron pellets, said Wednesday it closed a $750 million Series G to expand its Weirton, West Virginia manufacturing complex. The round pushed the company's lifetime funding above $2 billion.
Who's Writing The Check
T. Rowe Price led the round with new participation from Janus Henderson, Franklin Templeton, PEAK6 Investments, and Coatue. Returning backers included Sequoia Capital, Breakthrough Energy Ventures, TPG Rise Climate, Energy Impact Partners, Prelude Ventures, Engine Ventures, Capricorn's Technology Impact Funds, NGP, Gigascale Capital, Blindspot Ventures, M&G Catalyst Fund, GE Vernova, and Dustin Moskovitz and Cari Tuna. Form has now raised more than $2 billion since its 2017 founding.
Why AI Is Driving Iron-Air
Form's iron-air chemistry cycles between iron and rust to release and store energy, targeting duty cycles measured in days rather than hours. That profile fits the emerging demand from AI data centers, which increasingly want firm capacity to sit alongside solar and wind. The U.S. installed 9.7 GWh of battery storage in Q1 2026, up 32% year over year, and multi-day chemistries are pitched as the answer to when the sun doesn't shine for a week.
Weirton Ramp
The Series G will fund additional production lines at Form Factory 1, the rebuilt steel mill on the Ohio River that Form began commissioning in 2024. Co-founders Yet-Ming Chiang and Mateo Jaramillo have said the design is meant to hit sub-$20/kWh long-duration costs. The company follows other long-duration bets covered on The Robotics Media, including Ore Energy's $43M Series A for European iron-air production and Ore Energy's 1 GWh Budget Thuis deal.
What's Next
Form's earliest commercial project, a 1 MW/150 MWh pilot for Minnesota's Great River Energy, is due online this year. Utility contracts in Georgia, Colorado, California and Virginia line up behind it.
Reporting based on coverage from TechCrunch, Data Center Dynamics and Form Energy.