Fusion power startup Helion Energy has closed a $465 million funding round led by Thrive Capital, with participation from SoftBank Vision Fund 2, Lightspeed and others. The Series G values the company at $15.5 billion-nearly triple its valuation from January 2025.
Helion is developing a fusion reactor called Polaris, which generates electricity by fusing atomic nuclei. The process uses a D-He-3 fuel, turning it into plasma, compressing it with magnetic fields, and accelerating donut-shaped plasma rings toward each other at 100 million miles per hour. The collision creates conditions for fusion, and the resulting magnetic field changes produce an electric current.
The company plans to manufacture its own helium-3 fuel via deuterium-deuterium reactions. Helion says Polaris requires less shielding, cooling, and turbine equipment than other designs because it produces protons instead of neutrons and operates in discrete fusion events rather than continuous burn.
Helion started building its first commercial fusion power plant in Malaga, Washington last year. The facility is expected to generate 50 megawatts of electricity when it comes online in 2028. Proceeds from the new round will expand manufacturing and accelerate commercial rollout.