Helion has become one of the most closely watched fusion companies in the private market. The company announced a $425 million Series F in January 2025 that valued it at $5.425 billion post-money and brought total funding above $1 billion.
Its backers include SoftBank Vision Fund 2, Mithril Capital, Dustin Moskovitz through Good Ventures Foundation, and Sam Altman, who previously led Helion’s $500 million Series E round in 2021.
Axios reported that Altman has stepped down as Helion’s board chair, is no longer involved with the board, and has recused himself from the OpenAI deal discussions. That matters because Helion is not just another supplier candidate. It is one of the biggest private bets tied to Altman’s broader view that abundant energy will be essential to scaling AI.
The catch is that fusion still has not crossed the commercial finish line. Axios said Helion believes it is nearing scientific breakeven, a key milestone where the fusion process generates more energy than it consumes, but no private company has yet achieved that threshold. The OpenAI talks are also said to remain conditional, with major issues still unresolved, including where Helion would actually produce the power.
Helion already signed the world’s first fusion power purchase agreement with Microsoft in 2023, targeting delivery of at least 50 megawatts from its first plant by 2028. In July 2025, Helion said it had secured land and begun building the site for that first fusion power plant.
Google has taken a parallel path through Helion rival Commonwealth Fusion Systems. In June 2025, Google signed a deal to buy 200 megawatts from CFS’s first ARC plant in Virginia, a transaction both companies described as a major fusion milestone.
Disclosure: This article was edited by Estefano Gomez. For more information on how we create and review content, see our Editorial Policy.