OpenAI CEO Sam Altman’s stake in Helion Energy draws scrutiny in Musk trial and on Capitol Hill

Sam Altman faced pointed questions Tuesday about his personal financial ties to Helion Energy, the Everett, Wash., fusion startup that’s aiming to supply vast amounts of energy to both OpenAI and Microsoft to power future data centers for artificial intelligence.

Testifying in the Musk v. Altman trial in Oakland, the OpenAI CEO confirmed under cross-examination that he owns roughly one-third of Helion, a stake valued at approximately $1.65 billion as of late 2025, according to financial disclosures in the case.

Altman, who left the Helion board in March, said he consistently recused himself from OpenAI’s dealings with the fusion company. Asked by Musk’s lawyer Steven Molo to explain what that meant in reality, Altman said it covered “the decision to proceed and the final approval of terms.”

He noted that OpenAI has never bought or received any power from Helion but said a 2024 agreement was “a way for us to have the opportunity to do that in the future.” Altman said he was aware of a second agreement in March 2026 but was not familiar with its details.

He acknowledged that “a huge percentage” of his time at OpenAI is spent securing energy and compute resources, which he was previously doing while also chairing Helion’s board.

Helion has separately agreed to sell power from its first commercial fusion plant, under construction in central Washington, to Microsoft starting in 2028. Microsoft, OpenAI’s longstanding partner and one of its largest investors, is also a defendant in the case.

It was part of a broader argument by Musk’s attorney that Altman used his position at OpenAI to boost the value of his personal investments. Financial disclosures in the case showed that Altman has a stake of more than $2 billion in companies that do business with OpenAI.

Musk alleges in the lawsuit that Altman and other OpenAI leaders secured his donations to found OpenAI as a nonprofit before converting it into a for-profit venture, enriching themselves in the process. OpenAI and Microsoft, which is also a defendant, have countered that Musk supported the conversion and sought unilateral control of the company for himself.

Molo also pressed Altman on his role negotiating a $200 million data deal between OpenAI and Reddit while holding a significant personal stake in the social media company. Altman said the deal arose from mediation under threat of legal action and that the board asked him to participate because he had the most context.

The conflict-of-interest questions extend beyond the courtroom.

The House Oversight Committee sent Altman a letter on May 8 requesting documents related to OpenAI’s handling of potential conflicts, citing the Helion relationship specifically.

In the letter, the Oversight Committee said it wanted to ensure that “funds donated for charitable purposes are not diverted for unintended uses, such as artificially increasing the market value of other companies in which an executive or board member may hold an interest.”

A group of Republican state attorneys general separately called on the SEC to scrutinize the issue ahead of OpenAI’s planned IPO, the Wall Street Journal reported.

Helion did not immediately respond to a request for comment.

It’s not the only local company caught up in the issue. The WSJ also reported that Altman last summer approached Kent, Wash.-based rocket maker Stoke Space about partnering with OpenAI on data centers in space. Altman is an investor in Stoke through his family office.

Helion, founded in 2013, is developing technology to generate electricity from nuclear fusion, the process that powers the sun. No company has yet demonstrated that fusion can produce commercially viable power, but Helion has raised more than $1 billion from investors and broke ground last summer on its first plant in Malaga, Wash.

Altman has been one of the company’s biggest backers, personally investing $375 million in a $500 million round in 2021 and joining as board chairman in 2015, shortly after recruiting the company into the Y Combinator startup accelerator.

The Helion questions were part of a wide-ranging day on the stand for Altman. He also sparred with Musk’s lawyer over accusations of dishonesty from former colleagues and defended his decision to return to OpenAI after being fired by the board in November 2023 — saying he was “willing to run back into a burning building” to try to save the company and its mission.

GeekWire reported on today’s proceedings via the court’s audio livestream. 

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