Thea Energy raises a $100M Series B to build its Eos stellarator

Published 2026-07-18, dated to the event: this May round surfaced in our review queue late — recorded here because it changes the fusion funding table.

Thea Energy, the 2022 Princeton/PPPL spinout commercializing a planar-coil stellarator, closed a $100M Series B led by Thomas Tull's US Innovative Technology Fund, with Idemitsu Kosan, Emerald Technology Ventures and a dozen others participating. The money expands its magnet manufacturing with a second northern-New-Jersey facility and funds siting and construction of Eos, a large-scale integrated stellarator aimed at power-plant-relevant, steady-state fusion. The round followed the DOE's certification of Thea's Helios preconceptual design — the first milestone-program awardee to earn that distinction.

Why it matters

The stellarator — long the "harder but steadier" cousin of the tokamak — now has a US commercial champion with nine figures of funding, joining Europe's Proxima Fusion ($411M) in betting that steady-state operation beats pulsed machines to a practical plant. It's another data point in the record $4.48B year the FIA documented, and the DOE-certification detail matters more than its size: milestone-based public money validating private designs is the pattern that pulled SpaceX-era aerospace forward.

What to watch

Eos site selection and construction start, magnet production rates from the second facility, and whether DOE milestone certifications keep converting into private follow-on rounds across the program's awardees.