Key Takeaways:
Helion's unique approach to fusion — harvesting electricity directly from magnetic fields rather than steam turbines — has attracted $465 million in new funding as the startup races to deliver power to Microsoft by 2028.
Helion, the fusion energy company backed by OpenAI co-founder Sam Altman, said Thursday it raised $465 million in a Series G round led by Thrive Capital, valuing the Washington-based firm at $15.5 billion. The valuation nearly triples the $5.4 billion price tag from its Series F round in January 2025, reflecting surging investor appetite for zero-carbon power sources to feed AI data centers.
"The demand for clean, always-on electricity from hyperscale AI operators is unlike anything we've seen in the energy industry," David Kirtley, Helion's chief executive officer and co-founder, said. "This funding allows us to accelerate Orion and deliver on our commitment to Microsoft."
The round included new investors Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners and Ford Motor Executive Chair Bill Ford, alongside existing backers Lightspeed Venture Partners, Mithril Capital, SoftBank Vision Fund 2 and Good Ventures Foundation. Helion has now raised $1.5 billion since its founding in 2013.
Helion's technology differs from most fusion approaches. While competitors such as Commonwealth Fusion Systems use powerful magnets to contain superheated plasma and then convert the heat to electricity via steam turbines, Helion compresses fusion fuel with magnets and harvests electricity directly from the expanding magnetic fields — similar to how an electric vehicle's regenerative braking captures energy. The company's Polaris test machine reached temperatures above 150 million degrees Celsius using fusion fuel, a milestone Kirtley said validates the direct-electricity approach. Some physicists remain skeptical, in part because Helion rarely publishes in peer-reviewed journals. "We don't want to theorize about fusion," Kirtley said last year. "We just want to go build it."
Orion and the Microsoft Deal
Helion's first commercial power plant, Orion, is under construction in Malaga, Washington. The company has signed an agreement to supply electricity to Microsoft by 2028 and a separate deal with steelmaker Nucor to develop a 500-megawatt fusion plant. The timelines are aggressive — most fusion companies, including Focused Energy and Thea Energy, which announced $240 million and $100 million rounds last week respectively, do not expect commercial-scale operations until the mid-2030s.
Altman stepped down from Helion's board in March as the two companies began exploring a partnership "at significant scale," according to a statement at the time. The OpenAI chief remains a major Helion investor.
Fusion's Investment Frenzy
The fusion sector has become one of the most active areas of climate-tech investing. In February, Inertia Energy emerged from stealth with a $450 million Series A, and Type One Energy said it was raising $250 million for a Series B. The capital is flowing despite fusion's long development timeline, driven by the technology's potential to deliver near-limitless electricity from seawater and disrupt trillion-dollar energy markets.
For AI-focused technology companies, fusion offers a solution to the growing power demands of data centers. Goldman Sachs estimates AI-related electricity consumption could increase 100-fold by 2030, making long-term power purchase agreements with fusion developers an increasingly attractive hedge against volatile natural gas and renewable pricing.
Helion shares are not publicly traded. The company's rising valuation signals strong institutional conviction in fusion's commercial viability, though investors face a binary outcome: either the technology works at grid scale within this decade, or it doesn't. The Microsoft 2028 deadline will be the industry's first real test.
This article is for informational purposes only and does not constitute investment advice.
