Realta Fusion harvests electricity directly from fusion reaction

On June 19, Wisconsin-based fusion startup Realta Fusion conducted an experiment that successfully generated electricity directly from a fusion reaction. Using its demonstration fusion device, WHAM, the company believes it is the first private company to publicly demonstrate direct electricity conversion from a fusion reaction. During the experiment, the startup used a prototype electricity converter attached to the end of its reactor to harvest energy, generating multiple amps of electricity at 100 volts to power a few lightbulbs.

The milestone demonstrates a highly efficient alternative to traditional power generation. Kieran Furlong, co-founder and CEO of Realta Fusion, estimates that direct conversion is about 90% efficient. By comparison, steam turbines in today’s fission reactors are about 33% efficient. Realta plans to use deuterium-tritium, a fuel type for fusion reactors, in its commercial reactors. About 20% of the energy from these reactions is released as alpha particles, which are charged helium nuclei. By harvesting this energy directly, the startup can capture power from plasma, demonstrating what is possible.

This direct harvesting method allows reactors to recirculate the electricity they generate to power their own operations, such as heating the plasma. Every power plant consumes some of the power it produces simply to operate, and fusion reactors are no exception. Startups face the challenge of building reactors that produce more energy than they consume, and the efficiency boost from direct energy conversion is intended to make clearing that hurdle easier. “You’re basically able to recirculate the electricity,” said Furlong, who estimates that this circularity could boost a commercial scale power plant’s total output by 20% to 30%. He described the process of spinning a flywheel of electricity as highly beneficial.

While Realta is the first to publicly demonstrate the technology, other players are pursuing similar designs. Helion, a competitor startup backed by Sam Altman, also plans to deploy direct energy conversion in its reactor, though it has not yet demonstrated the capability publicly. Furlong noted that harvesting electricity directly from the reaction helps improve the economics of a reactor’s design. To fund its development, Realta previously raised $36 million in a Series A funding round led by Future Ventures in 2025, and the company is currently raising a new round.

Why it matters

Direct energy conversion addresses the critical economic hurdle for fusion power by allowing plants to recirculate energy, potentially increasing total output by 20% to 30%.