Sam Altman-backed Helion raises $465M for Microsoft fusion plant
▼ Summary
– Helion raised $465 million in a Series G funding round led by Thrive Capital, valuing the company at $15.5 billion, with total funding reaching $1.5 billion.
– The startup is racing to complete its first power plant, Orion, aiming to deliver fusion power to the grid as early as 2028 under a deal with Microsoft.
– Helion uses magnets to compress fusion fuel and plans to harvest electricity directly from the magnets, unlike most peers that use steam turbines.
– Some fusion experts are skeptical of Helion’s approach because the company does not frequently publish in peer-reviewed journals, limiting external theoretical scrutiny.
– The fusion sector has attracted significant investment recently despite long timelines, driven by fusion’s potential for nearly limitless, always-on energy.
Helion, the fusion startup chaired by Sam Altman, has secured $465 million in a new funding round, lifting its valuation to $15.5 billion. The company announced the Series G raise on Thursday, marking another major vote of confidence in its quest to deliver commercial fusion power.
The fresh capital arrives as Helion races to complete Orion, its first power plant. The startup is working under an aggressive timeline, aiming to supply fusion-generated electricity to the grid as early as 2028 if it can meet the terms of its contract with Microsoft. Helion last raised $425 million in January 2025, bringing its total fundraising haul to $1.5 billion.
Thrive Capital led the latest round, joined by new investors including Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, and Bill Ford. Existing backers such as Capricorn Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, Dustin Moskovitz through the Good Ventures Foundation, SoftBank Vision Fund 2, and a university endowment fund also participated.
Helion’s technology sets it apart from many fusion peers. Most competitors use either magnets or lasers to confine and compress superheated plasma, then rely on steam turbines to convert the resulting heat into electricity. Helion, however, uses magnets to compress the fuel and plans to harvest electricity directly from those magnets. When fusion occurs inside the reactor, the expanding plasma pushes against the magnetic fields, and that force can be drawn off as inductive current, similar to how an electric vehicle recaptures energy during braking.
This direct conversion approach could dramatically improve a fusion plant’s efficiency. Yet some fusion experts remain skeptical, partly because Helion rarely publishes in peer-reviewed journals, leaving physicists unable to scrutinize its theoretical foundation. CEO David Kirtley has dismissed those concerns, arguing that results from the company’s working devices will speak for themselves. “We don’t want to theorize about fusion,” he said last year. “We just want to go build it.”
Helion is not alone in attracting big checks. The fusion sector has become an investor magnet in recent months. Focused Energy and Thea Energy both announced new rounds last week, raising $240 million and $100 million respectively. In February, Inertia Energy emerged from stealth with a $450 million Series A, and the month before, Type One Energy said it was raising $250 million for a Series B.
These investments keep flowing despite fusion’s famously long development horizon. While several companies have hit key milestones recently, most predict their first commercial-scale plants won’t come online until the mid-2030s at the earliest. The appeal lies in fusion’s promise: nearly limitless, always-on energy from abundant seawater. For AI-focused tech giants, that’s a compelling draw. And if fusion companies can drive costs down aggressively, the technology could disrupt trillion-dollar energy markets. The timelines may be longer than venture capital typically tolerates, but the potential payoff could be far larger.
(Source: TechCrunch)