The promise of nuclear fusion power

WHEN SAM ALTMAN ARRIVED AT HELION ENERGY'S SMALL Redmond, Wash., office in early 2014, nuclear-fusion textbooks tucked under his arm, the company was focusing its efforts on research and development.

- BY HARRY BOOTH

By the time he left, several days later, he had persuaded the fusion-energy startup to chart a more aggressive path toward deployment, CEO David Kirtley recalls. A year later, Altman, who was co-founding OpenAI around the same time, invested $9.5 million in Helion, taking the role of chairman. He plowed a further $375 million into Helion in 2021, making it one of the largest personal bets in his multibillion-dollar portfolio.

Once a government-led pursuit, nuclear fusion is now a private-capital race, much of it financed by the same people building energy-hungry AI and pursuing the goal of creating systems with human-like intelligence, known as artificial general intelligence (AGI). The fusion-energy industry's total funding has jumped from $1.7 billion in 2020 to $15 billion as of September 2025, according to a report by E.U. body Fusion for Energy. Alongside Altman, who has said AI's future depends on an energy breakthrough, investors in Helion include OpenAI funder SoftBank as well as Facebook co-founder and early Anthropic backer Dustin Moskovitz. Nvidia has backed Helion rival Commonwealth Fusion Systems (CFS). So too has Google, which has also invested in another player, TAE Technologies.

“AI is a big driver [due to] the energy needs ... to power their data centers,” says Troy Carter, director of Oak Ridge National Laboratory's fusion-energy division.

Recent engineering progress and the flood of cash from investors willing to chase moon shots have some firms promising grid power within years rather than decades. They must still prove the technology works, but if fusion delivers, it would provide carbon-free power without solar and wind's seasonal fluctuations or nuclear fission's long-lived radioactive waste—a breakthrough that wouldn't just lower power bills, but reshape what's possible.