Fusion's 2026 Scoreboard: Helion Hits 150MºC, ITER Costs $22B, Thea Banks $100M

Two fusion companies announced technical and financial milestones within four months of each other in 2026. The numbers behind them say more about the state of the field than the press releases do.

Helion's Polaris machine reached 150 million degrees Celsius (150MºC), the company said on 13 February 2026, making it the first privately developed fusion device to demonstrate measurable deuterium-tritium (D-T) fusion. The Everett, Washington firm said Polaris is also the first and currently only private fusion machine to run on D-T fuel, a milestone it hit in January. Thea Energy, a stellarator developer spun out of Princeton University and Princeton Plasma Physics Laboratory in 2022, said on 27 May 2026 that it raised $100 million in Series B funding led by Thomas Tull's US Innovative Technology Fund.

What Helion actually demonstrated

Helion's announcement is specific about the number and careful about the fuel.

D-T fusion is the easiest reaction to achieve, which is why ITER and most public programmes use it. But D-T produces most of its energy as high-energy neutrons, and Helion has said its commercial machines will run on deuterium-helium-3 instead, a fuel it describes as suited to commercial operations. Polaris's D-T campaign is therefore a stepping stone, not the destination. The company said it will keep testing Polaris to reach optimal temperatures for D-3He.

The 150MºC figure broke Helion's own industry record of 100MºC, set by its sixth-generation Trenta prototype. Within the private fusion industry, 100MºC is treated as the threshold plasma temperature for a commercially relevant machine, so Polaris cleared a bar the sector had been chasing. Helion said it was also the first company to receive regulatory approval to possess and use tritium for the purpose of demonstrating fusion energy production.

Outside voices quoted in the announcement did not dispute the results. Ryan McBride, an inertial confinement fusion and pulsed power expert who has worked at Sandia National Laboratories and taught at the University of Michigan, said he reviewed diagnostic data and called the evidence of D-T fusion and temperatures exceeding 13 keV "exciting." Jean Paul Allain, associate director for Fusion Energy Sciences in the Department of Energy's Office of Science, said the data indicated "strong progress." He noted that getting fusion on the grid requires approaches that allow rapid turnaround in design and testing.

Helion began operating Polaris at the end of 2024. In July 2025 it started building on the site of Orion, its first commercial machine, in Malaga, Washington, which the company says will deliver electricity from fusion to the grid for Microsoft. The announcement gave no date for when that delivery begins, and no fusion gain figure for the D-T campaign.

Thea's bet on a different shape

Thea Energy's $100 million round, announced 27 May 2026, was oversubscribed. General Innovation Capital Partners, Linse Capital, Calm Ventures, Climate Capital, Divergent Capital, Emerald Technology Ventures, Gaingels, Idemitsu Kosan, Overlay Capital, Timescale Ventures and Whatif Ventures all took part, alongside existing investors including Alumni Ventures, Hitachi Ventures, Lowercarbon Capital and Prelude Ventures.

The company is commercialising the stellarator, a magnetic confinement architecture that predates the tokamak but was long considered impractical because its twisted 3D magnets are hard to build. Thea's approach replaces precision mechanical fabrication with arrays of mass-manufacturable planar magnets and software controls. Gaetano Crupi, a managing director at USIT, said in the announcement that prior 3D stellarator magnets made the system impractical, and that Thea's breakthroughs shift complexity from fabrication to software-defined controls.

The money will expand magnet manufacturing capacity, including a second facility in northern New Jersey, and support siting and construction of "Eos", a large-scale integrated stellarator intended to create power-plant-relevant steady-state fusion. Thea said it will select a site for Eos later this year and double its team. It aims to start construction of its first "Helios" power plant before the end of the decade, and says it is in discussions with more than a dozen power offtakers, hyperscalers and utility partners.

Thea is an inaugural awardee of the Department of Energy's Milestone-Based Fusion Development Program and holds six DOE INFUSE awards. The company said the DOE certified its Helios preconceptual design milestone, making it the first awardee to receive that distinction. It also said it built and operated the world's first superconducting magnet array capable of producing the complex magnetic fields required for commercial stellarator systems, and de-risked the full-scale planar shaping magnets for Eos.

ITER's arithmetic

Against those two, ITER is the counterexample: bigger, slower, publicly funded, and still the reference point for the field.

CNET reported in May 2026 that the International Thermonuclear Experimental Reactor, under construction in southern France, carries an estimated cost of $22 billion and is designed to contain plasma at 150 million degrees Celsius, ten times hotter than the core of the Sun. Containing that plasma requires superconducting magnets kept a few degrees above absolute zero, with only a thin heat shield between one of the hottest environments ever created and one of the coldest. Cracks in the heat shield's piping were found in 2020, along with welding distortions and COVID-19 disruptions. The problems led to a years-long delay and an additional $5 billion for repairs.

ITER's chief strategic advisor, Laban Coblentz, described the collaboration to CNET in blunt terms: that China and Russia would work with the US and Europe, plus Korea, India and Japan, is "either genius or insane." Javier Artola, a scientist modelling ITER's plasma behaviour, framed the project as public knowledge: "This is a publicly funded project. It is the knowledge of the world." Every member state of the ITER agreement, which includes more than 30 countries, gets access to the science, and non-members may benefit if members agree to share.

The case for ITER in a world of private startups is that it de-risks research and development for everyone. Every problem ITER solves is one private fusion companies do not have to. CNET's reporter came away arguing we may be living in the last decade when fusion is still spoken of as a distant dream.

Direct conversion, and what it does not prove

One smaller result deserves attention precisely because of how modestly it was framed. On 19 June 2026, Realta Fusion, working with the University of Wisconsin-Madison, became the first private fusion company to demonstrate direct energy conversion (DEC) of plasma kinetic energy into electricity, on the WHAM prototype device.

The converter was installed on WHAM's end-ring assembly, replacing the centre disk, and slows charged particles exiting through the mirror's loss cone using an electrostatic potential. The first prototype is a single-stage device with three meshed grids: an electrically grounded grid, an electron repulsion grid and an ion collector grid. It draws multiple amps of current at around 100 volts, which Realta says is enough to illuminate a few lightbulbs. The company plans to scale the voltage in the coming weeks.

Realta's post is unusually direct about the limits. It states that this is neither a demonstration of net electricity production nor large-scale conversion of fusion-born power into electricity, and that those milestones await future devices. WHAM is a prototype-scale magnetic mirror running on deuterium only, so most of the directly converted energy is input power the company supplied to heat and sustain the plasma. At Qsci = 5 in a D-T plasma, Realta says alpha power would become equal in magnitude to the input power needed for continuous operation.

The pitch for DEC is efficiency. In first-generation D-T plants, roughly 80% of yield arrives as high-energy neutrons and 20% as charged alpha particles. Neutrons are converted to heat in a moderating blanket and used as process heat or to spin turbines. Charged particles can be captured by DEC instead, skipping part of the thermal cycle that has inherent efficiency limits. Realta compares a DEC-equipped D-T plant to a hybrid powertrain: heat does most of the work, with an electric component improving overall efficiency.

Read together, the four results point in one direction and warn against one conclusion. Private fusion is now producing measurable physics, running on the fuel the field considers hardest, and attracting nine-figure cheques. It has not produced net electricity. None of the companies in this dossier claims otherwise, and the one that came closest to being able to, Realta, went out of its way to say it had not.