Why Really Tiny Nuclear Reactors Are Bringing In Big Money

Nuclear energy is making a comeback , conceptually at least. While we’re yet to see a whole lot of new steel in the ground, money is flowing into fusion , there’s a push to build more standard fission reactors , and the dream of small modular reactors lives on, even in the wake of the NuScale disappointment .

All this excitement generally revolves around nuclear’s potential to provide clean, baseload power to the grid. But Washington D.C.-based Last Energy is pursuing a different strategy — making miniature, modularized reactors to provide power directly to industries such as data centers, auto manufacturing, and pulp and paper production. Size-wise, think small modular reactors, but, well, even smaller — Last Energy’s units provide a mere 20 megawatts of electricity, whereas a full-size reactor can be over 1,000 megawatts. SMRs sit somewhere in between.

Today the company announced its $40 million series B round, led by the Austin-based venture capital firm Gigafund. Last Energy aims to deploy its first microreactor by 2026, and CEO and founder Bret Kugelmass told me the company has already reached commercial agreements for 80 units, all in Europe. Nearly half of these will be deployed at data centers, the notoriously energy hungry server farms powering the AI boom.

Kugelmass told me the goal is for Last Energy’s reactor to be transportable in the back of a truck. “We decided to focus most of our specific design criteria based on supply chain and logistics constraints,” he said. Every part of the system is “built in a factory, first tested in a factory, mass manufactured in a factory, and then snaps together like a Lego set out in the field.”

There are currently no operational microreactors anywhere in the Western world, though other companies, including Radiant, Westinghouse, and BWX Technologies are also trying to build one. Last Energy’s investors are betting, however, that it could be one of the first to market.

As of now, the company has reached the permitting stage for some of its European projects. Kugelmass told me that Wales, England, Poland, and Romania are the company’s top markets, and that the decision to start in Europe was mainly financial. “Energy is so expensive in Europe compared to the U.S. — I mean, we're talking like two, three times higher for the exact same thing that we're going to deliver. We can make two or three times more money.”

The company estimates that its reactors can be fully manufactured and assembled onsite within two years. And while Kugelmass wouldn’t reveal an exact price, he said Last Energy will be cost-competitive with solar or wind plus storage. Problem is, there’s not really any precedent that would indicate how realistic these targets are, and nuclear doesn’t exactly have the best track record when it comes to arriving on time or on budget.

At the very least, though, Kugelmass told me the reactor’s smaller size makes a meltdown “practically impossible,” meaning securing regulatory approval should be much simpler than it is for full-size plants. And building on the customer’s side of the meter also allows the company to supply power before it’s officially grid-connected, meaning Last Energy can work around the interminably long interconnection queues that plague the European clean energy market just as they do the U.S.

As manufacturing ramps, costs come down, and the U.S. Nuclear Regulatory Commission streamlines its process for approving new projects, Kugelmass told me he could see Last Energy entering the domestic market in a few years. After all, with American companies driving the boom in AI and cloud computing, the U.S. has far more data centers than anywhere else on earth. Last Energy has aggressive plans to meet that demand, aiming to deploy 10,000 reactors in the next 15 years.

“But it doesn't stop there, because that's still only like 1% of global energy,” Kugelmass told me, saying that Last Energy’s ultimate goal is to “fundamentally transform global energy.” But that’s for tomorrow. For the unglamorous now, some more prototypes and permits are in order.

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