Google’s push to run data centers on cleaner electricity is getting an expensive new tool: a “days-long” battery. Google said earlier this week it is building a new data center in Minnesota that will be powered by a mix of wind, solar, and a Form Energy battery designed to discharge for days at a time . The price tag for that battery system is about $1 billion.

What Google is buying?

Form Energy’s product is an iron-air battery that the company says can deliver a continuous 300 megawatts for 100 hours . The battery “works by breathing,” where oxygen pumped into the cells rusts iron, releasing electrons.

In Google’s Minnesota project, the battery is intended to smooth the flow of electricity coming from 1.4 gigawatts of wind power and 200 megawatts of solar power, a practical challenge when generation rises and falls with weather and daylight.

A milestone customer for Form Energy

For Form Energy, the Google deal reads like a turning point. The startup has worked on the technology for years and built a factory in West Virginia to produce the batteries, But it hadn’t landed a major customer until this recent deal with Google.

With that large order now on the books, Form Energy CEO Mateo Jaramillo told TechCrunch the company is in the process of raising a $500 million round. Form has raised $1.4 billion to date, and that the company plans to go public next year.

A $1 billion battery purchase, especially one built to run for 100 hours, underscores how seriously hyperscalers are looking at long-duration storage as they expand power-hungry infrastructure. In this case, Google is pairing renewables with a battery designed to keep power flowing not just for a few hours, but for multiple days.

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