In a breakthrough for commercial fusion energy, Wisconsin-based Realta Fusion announced that an experiment conducted on June 19 successfully powered a lightbulb using electricity harvested directly from WHAM, its demonstration fusion device. The company believes it is the first private entity to publicly demonstrate such a feat.
"We can take power from a plasma," Kieran Furlong, co-founder and CEO of Realta Fusion, told TechCrunch. The milestone shows "what's possible," he added.
The key innovation is direct energy conversion. While conventional fission reactors use steam turbines that are only about 33% efficient, Realta's direct conversion method is estimated at roughly 90% efficiency. The company built a prototype electricity converter and attached it to the end of its reactor, where it successfully harvested enough "alpha power" — charged helium nuclei from deuterium-tritium fusion — to generate multiple amps of electricity at 100 volts.
This is significant because every power plant must consume some of the power it produces just to operate. About 20% of the energy from deuterium-tritium fusion reactions takes the form of alpha particles. By capturing these directly, Realta's approach could recirculate electricity to heat the plasma, dramatically reducing the net energy needed from external sources.
"You're basically able to recirculate the electricity," Furlong said. He estimates that this circularity could boost a commercial-scale power plant's total output by 20% to 30%. "Spinning a flywheel of electricity, if you like, is very beneficial."
The breakthrough comes at a pivotal moment for fusion energy. Since the 2022 demonstration at the National Ignition Facility proved controlled fusion could generate more energy than it consumes, startups have raced to build commercially viable reactors. Realta's approach uses a magnetic mirror configuration in its WHAM device, a distinct path from the more widely known tokamak or stellarator designs.
Realta is not alone in pursuing direct conversion — Helion, backed by Sam Altman, also plans to use the technology but has yet to publicly demonstrate it. Realta previously raised $36 million in a Series A led by Future Ventures in 2025 and is currently raising a new round.
