Fusion Startup Helion Reaches $15.5B Valuation in $465M Series G Round

Quick Facts

• Helion Energy raised $465 million in Series G funding, tripling its valuation to $15.5 billion from $5.43 billion in January 2025
• The company achieved 150 million degree Celsius plasma temperatures and became the first private fusion firm to demonstrate deuterium-tritium fusion
• Helion signed a 2028 power delivery contract with Microsoft for 50 MW of fusion electricity to power a Central Washington data center

Fusion power startup Helion Energy closed a $465 million Series G funding round that values the company at $15.5 billion. The round nearly tripled Helion’s valuation from $5.43 billion in January 2025.

Thrive Capital led the Series G with participation from SoftBank Vision Fund 2 and Lightspeed. The funding brings Helion’s total capital raised to more than $1.5 billion. The deal marks the largest venture capital funding in the Pacific Northwest this year.

Helion achieved significant technical milestones with its Polaris prototype. The system became the first privately developed fusion energy machine to demonstrate measurable deuterium-tritium fusion and reach plasma temperatures of 150 million degrees Celsius. These temperatures broke Helion’s own commercial fusion industry record of 100 million degrees Celsius.

‘Fusion is no longer a future idea, but a path to clean, reliable, affordable always-on electricity at scale,’ said David Kirtley, Helion’s CEO. ‘This funding accelerates our ability to deliver on that promise.’

The company operates under an aggressive commercial timeline. Helion signed a contract with Microsoft in May 2023 to supply at least 50 MW of fusion electricity to a Central Washington data center by 2028. The agreement was the first commercial fusion energy contract ever signed.

Helion broke ground on its Orion facility in Malaga, Washington in July 2025. The eighth-generation system is designed to scale fusion results to grid-level electricity output. The site sits on land leased from Chelan County Public Utility District near the Rock Island Dam.

OpenAI CEO Sam Altman owns roughly one-third of Helion, according to testimony during the recent Musk v. Altman trial. Altman left the Helion board in March 2026. His early investment gave the company credibility when funding was scarce in the fusion space.

The broader fusion industry raised $2.64 billion in private and public funding in the 12 months leading to July 2025. That pace has accelerated in 2026, driven by AI’s demand for always-on, carbon-free electricity at scale.

Helion uses a magneto-inertial fusion approach that fires two plasma rings at each other at high speed. The company extracts energy directly through electromagnetic induction rather than heat conversion. This approach aims to be more efficient than competitors using tokamak designs.

Read more: Fusion power startup Helion valued at $15.5B in $465M funding round