100 Hours of Storage: Unpacking the Iron-Air Battery Deal That Changes Everything

Xcel Energy and Google recently announced a monumental clean energy agreement to power a new data center in Minnesota. While the deal includes massive wind and solar additions, the real game-changer is the energy storage component: 300 MW of iron-air batteries manufactured by Form Energy, boasting an unprecedented 100 hours of duration.

To put the scale into perspective, this single 30,000 MWh (30 GWh) project represents over 50% of the entire battery energy storage installed across the U.S. last year.

In our latest update, we unpack the details of this historic deal, including:

• The Iron-Air Technology: How the simple process of oxidizing (or rusting) cheap, abundant iron is being harnessed for grid-scale power.
• The Efficiency Trade-off: Why the market might be willing to accept a remarkably low 40% round-trip efficiency in exchange for the firm, dispatchable capacity required to balance variable wind and solar.
• Manufacturing Scale: How this single Google project will consume 60% of the 500 MW annual capacity at Form Energy's rehabilitated West Virginia steel mill.

Check out the full breakdown to explore whether this 100-hour battery is the key to solving the grid's resource adequacy challenges amid the booming, insatiable power demands of modern data centers.

Transcript

Clean Energy Tariff And New Buildout

Distributed Storage And Capacity Connect

300 MW Iron-Air Battery Reveal

Putting 30 GWh In Perspective

Form Energy’s Journey And Deals

Efficiency Tradeoffs And Promise

Outlook, Risks, And Closing

SPEAKER_00 0:03

I've got your energy stories for this, the first week of March 2026. Well, last week, XL Energy announced a deal to supply a new Google data center in Pine Island, Minnesota with renewable energy. The utility said it was committed to ensuring that new large loads did not negatively affect other ratepayers, and that this arrangement would reflect that commitment. To make that happen, we'll serve Google under a Clean Energy Accelerator Charge, CEAC, similar to a tariff arrangement under which Nevada's Envy Energy plans to deliver 115 megawatts of clean enhanced geothermal power to Google in that state. In this case, the CAC will result in development of 1,400 megawatts of wind and 200 megawatts of solar. It also provides for a$50 million investment towards Excel's Capacity Connect program, a unique effort developed jointly with DER provider Spark Fund, in which it will develop and own up to 200 megawatts of distributed storage assets strategically placed across its service territory at local commercial, industrial, and institutional sites. Each site will include batteries providing between one and three megawatts of storage if it gets approved by regulators. Ah, storage. Well, that is the last piece of this initial huge Google deal. To support its wind and solar and firm up the energy they produce, the project also includes something the world has never seen before: 300 megawatts of iron air batteries to be manufactured by Form Energy, boasting 100 hours of duration, putting that project at 30 gigawatt hours. Let's just put that 30 gigawatt hour number in perspective. In 2025, per the just released Solar Energy Industries Association and Benchmark Minerals Report, the U.S. installed over 57 gigawatt hours and 27 gigawatts of nameplate capacity. Two things stand out in the comparison here. First, the average duration of batteries installed across the U.S. last year was only two hours. So the foreign project, the duration will be 50 times the annual average. Second and most impressive, this single project represents a little over 50% of the entire battery energy storage they installed across the country last year. That's phenomenal. Form Energy CEO Mateo Hardomilo left Tesla years ago, and he set up a team at Form in 2017 to create longer duration storage capabilities. After exploring many materials, he settled on iron, which, when it oxidizes, another word for rusting, releases energy. Iron's abundant and it's cheap. So the company set about testing and validating its technology, and it was a long time coming. In 2020, I was excited to see Form announce a 1 megawatt, 150 megawatt hour project with Great River Energy in Minnesota because it felt like there was a there there. That project then got drawn out, although construction finally began last year in Cambridge, Minnesota, with the project now at 1.5 megawatts and 150 megawatt hours, as form eventually settled on the 100 hours as its sweet spot. The company subsequently signed two 10 megawatt, 1000 megawatt hour deals with Excel for utilities in Minnesota and Colorado, a 15 megawatt, 1500 megawatt hour deal with Georgia Power, and a 5 megawatt, 500 megawatt deal with the California Energy Commission. It looked to be on its way. But it still needed a factory and to prove it could actually manufacture products. So Form eventually bought and rehabbed an old steel mill in Wirgin, West Virginia, with a plan to create annual manufacturing output of 500 megawatts and 50,000 megawatt hours when fully built out. This Google deal will then take 60% of that capacity. One of the biggest questions, in addition to the company's ability to manufacture a reliable product, which is now proven to Excel after manufacturing something on the order of 100,000 electrodes, the anodes and the cathodes, meaning it's run 60 miles of electrode materials through the plant, while the other question was whether the market would be able to embrace a new technology with one significant drawback. Unlike lithium-ion batteries that typically operate at 90% round-trip efficiencies, RTEs, losing 10% of the energy during each cycle, or Pumphyro that often sits in the mid-70% RTE range, form has an abysmal 40% RTE. Sanger Neil Young once sang that Rust never sleeps, perhaps, but doesn't appear too energetic in this case with these low RTEs. Nonetheless, 100 hours of duration somewhat compensates for that drawback, especially if this technology can be delivered reliably and at low cost and in enormous quantity. Then it has the chance to become a proverbial game changer in today's so-called energy transition that relies greatly on variable wind and solar to decarbonize the grid. 100 hours gets you to dispatchability and firm capacity that the grid sorely needs in its quest to address the critical issue of resource adequacy, especially with the apparently insatiable demand from new data centers. Part of my job as an author, keynoter, and educator is to look at the technologies of tomorrow and speculate where they might take us. Given that role, I've been excited about Forum Energy for some time. And in 2024, I began including a slide showing Forum Energy in some of my keynotes and workshops related to resource adequacy and data central loads. I even had conversations with members of the Forum team where they diplomatically indicated that data load was of great interest. But then, even as forecasted data load soared, there were crickets from the company, and I began to fear that perhaps I was a little over the tips of my skis on this one, speculating about something that would eventually prove to have no substance. Most of the time, I guess right. But I was beginning to feel some unease on this one. So it was with some relief when I read the announcements last week from Excel, Google, and Form. Now the critical questions, in the face of this enormous new electricity demand from data centers and a growing need to firm up renewables, the question is whether Form Energy can deliver to the broader market at an attractive price point and whether it can scale to the gigawatts of capacity and hundreds of gigawatt hours of energy storage capability needed in the very near future. In the meantime, I'm briming with gratitude on the news of this deal, as at least for this week, it's kept me from looking like a fool. Well, thanks for watching, and we'll see you again soon.