Helion raises $465 million to advance fusion power plant

Helion, the fusion startup backed by Sam Altman, announced on Thursday that it has raised $465 million in a Series G funding round. The late-stage funding round, led by Thrive Capital, brings Helion’s total funding raised to $1.5 billion and values the company at $15.5 billion. The startup previously raised $425 million in a funding round in January 2025.

The company is racing to complete Orion, its first power plant, with the goal of deploying fusion power to the grid as early as 2028 under a partnership with Microsoft. Helion’s approach to fusion power differs from many of its peers. While other companies plan to use steam turbines to transform intense heat into electricity, Helion intends to harvest electricity directly from the magnets used to compress the fuel. When fusion occurs in the superheated plasma inside the reactor, the plasma expands and pushes against the magnetic fields. This force is then drawn off the magnets as electricity, similar to how an electric vehicle reverses its motors to provide braking force and recharge its battery.

While Helion pushes forward with its timeline, some fusion experts are skeptical it could work. This skepticism is partly because Helion, unlike many of its competitors, does not frequently publish in peer-reviewed journals, meaning physicists have not been able to examine the theoretical underpinnings of its technology. David Kirtley, Helion’s CEO, argues that eventual results from the company’s fusion devices should be sufficient. “We don’t want to theorize about fusion,” Kirtley said, emphasizing the company’s focus on building physical systems.

Helion’s funding reflects a broader investor appetite for fusion energy, despite the lengthy timelines typically associated with commercializing the technology. Several of Helion’s peers have also secured funding rounds recently:

• Focused Energy announced a $240 million funding round last week.
• Thea Energy announced a $100 million funding round last week.
• Inertia Energy emerged from stealth in February with a $450 million funding round.
• Type One Energy is in the process of raising $250 million for a funding round.

Why it matters

Fusion energy is increasingly viewed as a critical solution for the massive power demands of AI, though the sector faces a long road to commercial viability and significant technical scrutiny.