Nuclear startup Helion hits $15.5 billion valuation in latest funding round

Nuclear fusion energy company Helion said on Thursday it raised $465 million in its latest funding round, led by Thrive Capital, valuing the Washington-based firm at $15.5 billion after the investment.

The round nearly triples Helion’s valuation from its last Series F funding round in January 2025, when it raised $425 million at a valuation of $5.4 billion.

The financing underscores surging demand for electricity to power massive data centers dedicated to artificial intelligence operations.

It also brings Helion’s total funding to $1.5 billion. The company said proceeds from the latest round will be used to accelerate commercial deployment, expand manufacturing capacity and support delivery of clean electricity to customers.

Helion, backed by OpenAI co-founders Sam Altman and Greg Brockman, is among dozens of public and private companies working to crack fusion’s core challenge: generating more electricity from the reaction than is required to start and contain it.

Investors in the latest Series G funding round included Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners and Ford Motor executive chair Bill Ford.

Existing backers including Lightspeed Venture Partners, Mithril Capital, SoftBank Vision Fund 2 and Good Ventures Foundation also took part in the funding.

The funding comes after Helion announced its Polaris test machine used fusion fuel and reached temperatures above 150 million degrees Celsius.

In 2023, the company signed agreements with Microsoft to supply electricity by 2028 and Nucor to develop a 500MW fusion power plant.

Earlier this year, OpenAI’s Sam Altman stepped down from Helion’s board as the companies start to explore working together “at significant scale”.

Helion was founded in 2013 by David Kirtley, John Slough, Chris Pihl, and George Votroubek. Its first power plant, Orion, is under construction in Malaga, Washington.

(By Pranav Mathur; Editing by Diti Pujara)