Helion, a fusion startup backed by Sam Altman, raises $465M to build a Microsoft powerhouse.

Helion, a fusion startup founded by Sam Altman, announced Thursday that it has raised $465 million in a new funding round that values ​​the company at $15.5 billion.

Investments are falling as Helion races to complete Orion, its first power plant. The startup has set an aggressive timeline for adding fusion power to the grid, as early as 2028 if it can deliver on the terms of its agreement with Microsoft.

The last startup raised $425 million by January 2025. In total, Helion said it has raised $1.5 billion.

The new round, Series G, was led by Thrive Capital with a long list of participants, including new investors Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, and Bill Ford, as well as existing investors, including Capricorn Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, Dustin Montures and Vionk Bantures. university fund.

Helion’s approach to fusion power is different from many of its peers. Some use magnets to contain the super-hot plasma needed for fusion conditions, while others use lasers to pressurize the fusion fuel until it reacts. In both cases, most of the startups plan to use steam engines to convert the excess heat into electricity.

But Helion, which uses magnets to compress fuel, aims to harvest electricity directly from the magnets themselves. When fusion occurs in the plasma inside the reactor, it expands, pushing against the magnetic fields. That energy can be extracted from the magnet as electricity, similar to how an electric car can reverse its motors to provide braking power and recharge the battery.

Such a configuration can greatly improve the efficiency of a combined power plant. But some fusion experts doubt it would work. That’s partly because Helion, unlike many of its competitors, rarely publishes in peer-reviewed journals, so physicists haven’t been able to nail down the theoretical foundations. David Kirtley, CEO of Helion, says that the final results from the company’s fusion equipment should be sufficient. “We don’t want to talk about fusion,” he told me last year. “We just want to go build.”

Helion is not alone in attracting new funding. The fusion sector has become an attractive investment in recent months. Focused Energy and Thea Energy both announced new rounds last week: Focused at $240 million, Thea at $100 million. In February, Inertia Energy went public with a $450 million Series A, and last month, Type One Energy said it was in the process of raising $250 million in a Series B.

Investments have come in strongly despite the long timeline for the merger. While several companies have made progress in recent months on steps they say pave the way to an efficient power plant, most predict they won’t start operating their first power plant until the middle of the next decade at the earliest.

Part of the appeal of fusion power is to deliver nearly unlimited amounts of sustainable energy using ocean water. For tech companies focused on AI, that’s an attractive proposition. But it also has the potential to disrupt other trillion-dollar energy markets if fusion power companies can’t lower costs. The timelines may be longer than what VCs are used to, but the potential profits can be huge.