Form Energy and its iron batteries

Form Energy is a company founded in 2017 and headquartered in Somerville, Massachusetts, United States. It specializes in developing long-duration energy storage solutions using batteries made primarily from iron, a metal that is far more abundant and cheaper than the lithium used in traditional batteries. The company’s technology relies on a process called reversible rusting: during discharge, oxygen from the air converts iron into rust, releasing electrons to power the grid. When charging, an electric current reverses the process, turning rust back into iron metal. This approach allows the batteries to store energy for up to 100 hours, significantly longer than the 4 to 6 hours typical of lithium-ion batteries. Form Energy’s goal is to make its batteries cost-competitive with natural gas, aiming for a price of $20 per kilowatt-hour, though the current cost has not been disclosed.

Solar and wind energy are now cheaper than fossil fuels in most places, but their output fluctuates depending on weather, time of day, and season. This variability creates a challenge for grid operators, who must ensure a steady supply of electricity even when renewable sources are not producing enough. Currently, many utilities rely on natural gas plants to fill these gaps, especially during extreme weather events like heat waves or deep freezes. Lithium-ion batteries, the most common storage technology, are expensive and typically designed to store energy for only 4 to 6 hours, which is insufficient for multi-day supply-demand imbalances. Form Energy’s iron-based batteries aim to address this gap by providing long-duration storage, allowing renewable energy to be stored and used when needed, reducing dependence on fossil fuels.

Form Energy has made significant strides in commercializing its technology. In 2027, it plans to deploy its first commercial project: a 150 megawatt-hour (MWh) battery system for Great River Energy, a Minnesota-based electricity provider. The company has also signed a larger deal with Xcel Energy, another Minnesota utility, to supply 30 gigawatt-hours (GWh) of batteries to power a new Google data center. This project, expected to come online in phases between 2028 and 2031, could become the world’s largest battery project by energy capacity once completed. To meet these commitments, Form Energy is scaling up production at its factory in West Virginia, which currently has a capacity of 2 GWh per year. The company has raised over $2 billion in financing, including grants from West Virginia and the U.S. federal government, to support its expansion.

Form Energy’s technology could play a key role in reducing global carbon dioxide emissions by enabling greater reliance on renewable energy. Many grid operators currently depend on natural gas plants to balance supply and demand, especially during periods of low renewable output or high demand. By providing long-duration storage, Form Energy’s batteries could help cover multi-day supply-demand imbalances, such as those caused by extreme weather or seasonal variations in sunlight and wind. Additionally, the technology could mitigate the environmental impact of the growing energy demand from AI data centers, which has already led to the delay of coal plant closures, the construction of new natural gas plants, and increased electricity prices for consumers. Cheaper energy storage could allow renewables to meet more of this increased demand.

The long-duration energy storage market is still in its early stages, and Form Energy faces competition from other technologies, including pumped hydropower, compressed gas, fuel cells, gravitational devices, and flow batteries that store energy in liquids. While the economics of multi-day batteries are complex—requiring large upfront investments but often sitting idle—Form Energy’s technology has attracted significant interest, particularly from data center developers. However, the company must prove it can deliver on its promises. Its current production capacity of 2 GWh per year is far below the 80 GWh it has committed to through commercial agreements. Another challenge is the physical footprint of the batteries, which are stacked in enclosures the size of shipping containers and require an acre of space for every 2 to 3 megawatts. For example, the Google data center project in Minnesota would occupy the equivalent of at least 75 football fields.