Helion Energy had been working toward a promised energy breakthrough but fell behind schedule and began running short on cash. The company's financial strain led to a high-profile fundraising effort in which Sam Altman, one of its largest investors, solicited OpenAI to lead a $500 million round at a $35 billion valuation. A significant portion of Altman's personal net worth is reported to be tied to Helion. Within the company, employees who reviewed the proposed financing raised doubts about the viability of the technology. Concern about potential legal exposure led some staff to avoid discussions about the deal in internal Slack channels. The article does not provide revenue, user, or other operating metrics, nor does it detail specific product plans beyond the referenced "energy breakthrough."

Total raised

$1.5B

Funding rounds

9

Latest round

Series G

Latest activity

Jun 2026