Helion Energy, a clean energy company aiming to commercialize “fusion energy” technology it says will be able to produce zero-carbon electricity, raised $500 million in a private fundraising round.

The funding, which was announced Friday, will go toward building a new prototype of its fusion generator in Everett, where the company is based, and manufacturing many of the expensive components it needs to make the generator work.

“[T]he magnitude of this funding and the vote of confidence that we got from a lot of smart people … lets us go off and focus so that we can get that electricity as soon as possible,” said David Kirtley, CEO of Helion.

The financing was led by Sam Altman, former president of Silicon Valley’s most renowned accelerator, Y Combinator. Altman is Helion’s executive chairman. In an interview, Altman said it was the biggest investment he had ever made.

Dustin Moskowitz, who co-founded Facebook (now Meta), and Mithril Capital, founded by billionaire Peter Thiel, also participated in the financing.

“My general philosophy on hard-tech investing is that you start with small investments,” Altman said. “But then once the technology works and once there is a plan to … make it work better at scale, then you put in a lot of money.”


Helion’s last financing in 2020 raised $40 million. In June, Helion said it had become the first private company to create the extraordinarily high temperatures in a chamber ― more than 100 million degrees Celsius ― necessary for fusion to occur.

With this new cash infusion, Kirtley said the company will have enough to build the first fusion generator by 2024 that outputs more electricity than it inputs. If it succeeds in hitting that target, the company will have the opportunity to secure an additional $1.7 billion from investors to begin building fusion generators for commercial use.

Fusion energy is created when two atoms are fused together at temperatures higher than 100 million degrees Celsius, releasing energy that can then be converted into electricity. Fusion is not to be mistaken with “fission,” which splits atoms and produces power using a nuclear reactor. Unlike fission, fusion does not produce any long-lived, dangerous radioactive byproducts, according to the company.

At a ceremony in July to break ground on the site where its fusion generator will be built, Helion also said it would be building the capability to produce a novel form of helium necessary for fusion to occur. At the ceremony, Kirtley said that commercial production of this specialized helium, called Helium-3, has not been done before on Earth. (Helium-3 is exceedingly rare on Earth, and is more abundant on the moon).

Helion is not the only Washington company to play in the fusion space. Zap Energy and CTFusion are also active with fusion technology that was born out of research at the University of Washington.