Form Energy

A steel town, a new kind of factory

Form Energy is no longer a lab demo with a good story. As of 2026 it is a manufacturer. Its first high-volume plant, Form Factory 1, occupies the ground where the Weirton Steel mill once stood in West Virginia - 550,000 square feet of it - and the first commercial iron-air batteries have already left the loading dock, bound for a utility cooperative in Minnesota.

The company employs close to a thousand people across West Virginia, Massachusetts, and California. It has raised more than $1.3 billion. And it sells exactly one thing: a battery that stores electricity for up to 100 hours, designed to keep a renewable grid running through the long, windless, sunless stretches that wreck the math on lithium-ion.

The grid has a clock problem

Here is the inconvenient truth about clean energy: the wind stops and the sun sets on a schedule that has nothing to do with when people want electricity. Lithium-ion batteries, the workhorses of the storage boom, are very good at covering a few hours - the evening ramp, the morning peak. They are punishingly expensive at covering days.

That gap is the whole problem. A grid running mostly on solar and wind needs something to lean on during a cloudy, still week in February. The conventional answer has been to keep a gas plant idling in the background, just in case. Form's founders thought that answer was both expensive and a little absurd - paying for fossil insurance on a clean system.

Five veterans and a chemistry nobody wanted

Form Energy came together in 2017 when two startups discovered they were chasing the same idea and merged. The founding cast is unusually credentialed for a hardware company: Mateo Jaramillo, who had built Tesla's energy-storage business; Yet-Ming Chiang, the MIT professor behind a string of battery companies; Ted Wiley; William Woodford; and Marco Ferrara.

Their bet was contrarian. Instead of chasing ever-fancier materials, they reached for the cheapest, most abundant metal on the planet and embraced a reaction most engineers spend their careers preventing. The pitch, roughly: what if rust were a feature?

Reversible rust, at grid scale

An iron-air cell is almost insultingly simple in concept. When it discharges, iron meets oxygen from the air and rusts, releasing energy. When it charges, an electric current reverses the reaction, converting the rust back into metallic iron and breathing the oxygen out. Iron, air, and a water-based electrolyte. No cobalt, no nickel, no supply chain that runs through a geopolitical minefield.

The cells are roughly a meter square. About fifty of them stack into a module the size of a household appliance, sitting in liquid electrolyte. String enough modules together and you get a power plant that can discharge for 100 hours - and, Form claims, at something close to one-tenth the cost of lithium-ion per unit of energy stored. The tradeoff is honesty itself: iron-air is slow and heavy, useless for a phone or a car. For a stationary grid asset that just needs to be cheap and patient, slow and heavy is fine.

The hard part was never the idea. Iron-air chemistry has been studied for decades and abandoned more than once, usually because nobody could make it last. Form's real work has been engineering - getting the cells to survive thousands of charge cycles without degrading, and then figuring out how to stamp them out by the millions at a price the grid can stomach. The company also writes its own modeling software, sometimes called Formware, to tell utilities exactly how much multi-day storage a given system needs and when it pays for itself. The battery is the product; the math is the sales pitch.

The utilities are buying

A clever chemistry is worth nothing if no one orders it. Form's answer to the skeptics is a customer list of conservative, risk-averse electric utilities - the kind of buyers who do not sign for unproven hardware on a whim.

Behind those names sits a pipeline the company puts at more than 750 MW / 75 GWh under agreement, plus projects with NYSERDA, the California Energy Commission, and an 85 MW / 8,500 MWh project in Maine backed by the U.S. Department of Energy.

Reshaping the system, not just selling a box

Form frames its work in unusually large terms - reshaping the global electric system - and backs it with a set of stated values it likes to repeat: humanity, excellence, creativity. The choice of Weirton was part of that story. Building iron batteries on the site of a shuttered steel mill is the kind of symbolism that writes its own headline, and the company has leaned into the promise of factory jobs in a town that lost them.

There is some irony in a climate company resurrecting a steel mill, and Form seems comfortable with it. The same iron that once built America's bridges is now being asked to hold its electricity. The choice also hedges a quieter risk: domestic supply. A battery made of iron and air does not need a cobalt mine or a lithium contract, which means a factory in Appalachia can plausibly source most of what it needs close to home - a selling point that has only grown louder as governments fret about where their clean-energy hardware comes from.

The boring battery wins by being boring

Form Energy is not a sure thing. Long-duration storage is a crowded, unproven market, and the company is racing to prove that a chemistry that works in a demo also works by the thousand, on budget, for twenty years. Competitors from Eos to ESS to Hydrostor are chasing the same gap with zinc, iron-flow, and compressed air.

But the appeal of Form's pitch is precisely that it is unglamorous. It does not depend on a breakthrough material or a mine in a faraway country. It depends on iron being cheap and rust being reversible - two facts that are unlikely to change. If a renewable grid is going to survive its worst week, it will need something dull and dependable standing behind it.

So return to that stack of cells in Minnesota, quietly rusting and un-rusting on a schedule the weather can't dictate. A decade ago it was a slide in a pitch deck. Now it is hardware on a grid, and the question Form Energy set out to answer - what backs up a clean grid when the wind dies for days - finally has a working reply made of iron and air.