Signals Inbox·August 22, 2026·Nuclear

Helion vs. CFS: who is ahead now?

CFS is ahead in the fusion race overall today, but Helion is ahead in the narrower race to get a commercial plant built first. The gap comes down to a simple split: Helion has moved faster into deployment, while CFS has retired more of the technical risk.

Q1Why do Helion and CFS keep getting compared in the fusion race?

Helion and Commonwealth Fusion Systems keep getting compared because they are currently the two strongest private U.S. candidates to turn fusion into a real electricity business, and they are taking almost opposite routes to get there.

CFS came out of MIT and is building SPARC, a compact high-field tokamak using powerful high-temperature superconducting magnets. SPARC is supposed to prove that this approach can produce more fusion power than the external power used to heat the plasma. The commercial machine comes next: ARC, a roughly 400 MW power plant planned in Virginia for the early 2030s.

Helion has chosen a much shorter development sequence. Its Polaris prototype uses field-reversed configuration, or FRC, plasmas that are formed, accelerated, merged and compressed in rapid pulses. Helion also wants to recover energy from the plasma directly through its electrical system rather than first turning fusion energy into heat and running a conventional turbine.

The commercial strategies now overlap as much as the science. Helion has a power purchase agreement with Microsoft and has already started building Orion, its first power plant. CFS has sold future ARC electricity to Google and Eni and is preparing the Virginia project while finishing SPARC.

Lately, the comparison has become even harder to ignore. Polaris is operating. Orion is under construction and has received its key Washington radiation licenses. On the other side, SPARC assembly is around 80% complete, CFS has cleared two more Department of Energy milestones for ARC, and the company recently raised another $1 billion.

Both companies now look much closer to infrastructure developers than speculative fusion startups. The interesting part is that they are taking very different risks to get there.

Q2Why is it still hard to say who is winning, Helion or CFS?

Helion is ahead in physical deployment today, while CFS is ahead in how much of its technical case has already been de-risked and checked from the outside.

That split explains most of the confusion around this comparison.

Helion can point to an operating seventh-generation machine and a commercial site where construction has already begun. CFS cannot. SPARC has yet to produce plasma, and construction of the commercial ARC plant comes later.

CFS can answer a different set of questions much more convincingly. Its core tokamak physics is built on decades of operating data. Its SPARC performance case has been published in detail. Its magnet technology has gone through physical testing and DOE review. The commercial ARC design now has its own five-paper physics basis.

Helion still asks us to accept more extrapolation between Polaris and a working power plant. Polaris has produced fusion, but Helion has yet to publish the electricity-from-fusion result that would connect its prototype directly to the central promise of Orion.

We therefore give more weight today to three things: what has actually been demonstrated, how much uncertainty remains before commercial electricity, and whether the company has enough capital and engineering capacity to survive the problems that will inevitably appear.

Helion vs. CFS scoreboard today

Q3Which company has the more advanced fusion machine right now, Helion or CFS?

Helion has the more advanced operating fusion machine today because Polaris is already running fusion experiments, while CFS is still assembling SPARC.

Polaris is Helion's seventh prototype. Helion recently reported that the machine produced measurable deuterium-tritium fusion and reached plasma temperatures of 150 million degrees Celsius. An outside fusion expert, Ryan McBride, reviewed diagnostic data and confirmed seeing evidence consistent with those results.

There is a useful historical pattern here. Helion has built seven machines rather than spending its entire history developing one giant device. Trenta, its previous prototype, had already crossed 100 million degrees. Polaris then moved to higher temperatures, D-T operation and a more complete electrical system.

CFS has much less integrated-machine history as a company. SPARC will be its first tokamak, although the design benefits from decades of tokamak work at MIT and across more than 150 machines built globally.

SPARC itself is now far beyond the renderings stage. According to the latest Fusion Industry Association survey, assembly is around 80% complete. Vacuum-vessel sections are being assembled, major support systems are going through commissioning, and production magnets are moving into Tokamak Hall.

Still, an operating machine beats an almost-finished machine on this specific question. Helion leads here today.

Q4Has Helion actually shown that Polaris can make electricity from fusion?

Helion has shown fusion inside Polaris, but it has yet to publicly demonstrate the electricity-from-fusion result that would validate the most important part of its power-plant architecture.

This distinction is easy to lose when reading headlines about temperatures and D-T fusion.

Helion's core commercial idea depends heavily on direct energy recovery. After its FRC plasmas collide and are compressed, the expanding plasma pushes back against the magnetic field. Helion plans to capture part of that energy electrically through electromagnetic induction.

The attraction is obvious. A conventional D-T reactor such as ARC captures most fusion energy as heat, then converts that heat into electricity. Helion wants a much shorter path from plasma energy to electrical output.

Polaris was originally presented in 2021 as a machine that would demonstrate "net electricity" in 2024. Helion now says that wording was too ambiguous and defines the Polaris goal more precisely: make fusion energy and convert a portion of it back into electricity on the capacitor bank.

That result has yet to be announced.

Helion's current FAQ is unusually clear about what remains. It lists "demonstrating electricity from fusion" among the most important outstanding steps, alongside repeatability, component lifetime, fuel processing and scaling the integrated system.

So we should give Helion full credit for what Polaris has actually achieved while keeping the biggest missing result separate. D-T fusion at 150 million degrees is impressive. Commercial electricity requires another step.

Q5Which fusion approach has more evidence behind it today, CFS's tokamak or Helion's FRC?

CFS's high-field tokamak has much more external evidence behind it today than Helion's FRC approach, and this is one of the biggest reasons we currently put CFS ahead overall.

The SPARC case is unusually inspectable for a private fusion program.

In 2020, a large team published seven peer-reviewed papers laying out the SPARC physics basis. The reference design targets fusion gain above Q=2 even under conservative assumptions. Under the nominal assumptions used in the main design paper, SPARC was projected around Q=11 and roughly 140 MW of fusion power.

Nobody should treat those projections as experimental results. The value comes from knowing exactly what CFS expects before the machine turns on and having enough detail for other plasma physicists to challenge the assumptions.

CFS has followed the same strategy with ARC. Five peer-reviewed papers published in 2026 examine the plasma performance, stability, disruptions, heat exhaust and overall physics basis of the commercial plant. The Department of Energy has also used CFS in its Milestone-Based Fusion Development Program, and CFS recently cleared two additional milestones covering ARC's preconceptual design and technology roadmap.

Helion has published peer-reviewed work on FRC compression, including a 2023 paper by David Kirtley and Richard Milroy. The public record is much thinner, especially for Polaris performance.

That becomes important when experts disagree. A group led by Karl Lackner at the Max Planck Institute published a formal critique this year of assumptions in Helion's D-He3 reactor analysis, particularly the treatment of ion and electron temperatures. Helion argues that its extremely short pulses change the relevant physics enough to preserve the required conditions.

Scientific American also interviewed John Slough, whose earlier FRC research helped lead to Helion. Slough now questions whether Helion can avoid the confinement and instability problems that have historically made FRCs difficult. Helion rejects his conclusions.

We cannot settle those disputes from theory alone. Polaris can settle them with better performance data.

For now, CFS asks us to believe fewer things that only CFS itself can verify.

Q6Which company has solved more of the hard problems needed for a real fusion power plant?

CFS has solved more of the upstream physics and magnet problems so far, while Helion has moved further into the practical job of building a commercial site.

CFS's biggest early bet was the magnet. The company needed high-temperature superconductors to generate magnetic fields strong enough to make a compact tokamak practical. CFS and MIT demonstrated a 20-tesla large-bore magnet, then moved from that test into a dedicated magnet factory and production hardware for SPARC.

The remaining problems are still ugly. ARC will need to manage enormous neutron loads, remove extreme heat, breed and process tritium, protect superconducting magnets and maintain components that sit close to a fusion plasma. CFS's latest ARC papers spend considerable time on disruptions and heat exhaust because those problems are central to whether a tokamak can become an economical power station.

Helion avoids several pieces of that architecture. Its FRC machine has simpler magnetic geometry, and direct energy recovery could reduce the amount of conventional power-plant equipment around the fusion core. Its eventual deuterium-helium-3 fuel cycle is also designed to reduce the high-energy neutron burden.

Helion pays for that simplicity elsewhere. The company needs sufficient confinement during extremely fast pulses, reliable merging and compression, high repetition rates, durable pulsed-power hardware and an energy-recovery cycle that works over and over again.

The key difference is where the uncertainty sits. CFS's most frightening problems now lean heavily toward reactor engineering. Helion still carries more uncertainty inside the fusion cycle itself.

At this stage of the race, we prefer CFS's problem set.

Q7Who is closer to a real commercial fusion plant, Helion or CFS?

Helion is physically closer to a commercial fusion plant today because Orion is already under construction and has moved further through the operating-permit process than CFS's ARC project.

Helion started site work in Malaga, Washington, in 2025. Chelan County later approved the next construction phase for the fusion-generator building. More recently, the Washington Department of Health issued Orion a Radioactive Materials License and a Radioactive Air Emissions License.

Those licenses are particularly useful evidence because a regulator has now examined real facilities, personnel and safety programs rather than a future project description.

CFS has also moved well beyond simply choosing a spot on a map. Its Fall Line Fusion Power Station in Virginia has received a conditional-use permit, and CFS has formally applied to connect the planned 400 MW ARC plant to PJM, the regional grid operator. Grid interconnection can take years, so doing that work early is exactly what a serious power developer should be doing.

The sequence is different. CFS wants SPARC to retire a large chunk of ARC risk before it starts building the commercial plant. The latest industry survey says SPARC should de-risk 13 of the 17 systems CFS considers necessary for ARC.

Helion has chosen more parallel development. Polaris testing, Orion construction, permitting and manufacturing expansion are all happening while the core electricity demonstration is still being pursued.

That makes Helion's physical lead very real. It also makes the next two years far less forgiving.

Q8Who has the stronger fusion customers, Helion or CFS?

CFS currently has the stronger overall book of power buyers, while Helion has the single most aggressive customer commitment in the industry.

Helion changed the commercial fusion market when Microsoft agreed to buy power from its first plant. Orion is designed to begin initial operations in 2028 and eventually deliver at least 50 MW. Scientific American reported that the agreement includes financial penalties for nondelivery, which makes it much more meaningful than a promotional partnership.

Helion also has a much larger development agreement with Nucor. The two companies are working toward a 500 MW fusion plant for a steel facility, and Nucor invested $35 million in Helion. The project originally carried a 2030 target, although the companies still need to establish a firm schedule.

CFS has since assembled a broader commercial portfolio around ARC.

Google has agreed to buy 200 MW from the Virginia plant, equal to half of ARC's planned 400 MW output. Eni then signed an offtake agreement worth more than $1 billion. Both companies have also invested in CFS, so they have exposure on both sides of the relationship.

We give CFS a narrow lead because two sophisticated energy buyers have committed around the same first commercial plant, with Google taking an unusually large share of its planned capacity.

Helion's Microsoft agreement remains the harder commitment to execute because the delivery timetable comes much sooner.

Q9Can we trust Helion's 2028 and CFS's early-2030s fusion timelines?

We trust CFS's timetable more today, even though Helion is aiming to reach the grid several years earlier.

Fusion schedules have a terrible history, so the useful question is how the companies behave when a milestone slips.

CFS once expected SPARC to demonstrate net fusion energy around 2025. Its current plan puts scientific breakeven in 2027. A two-year delay is significant, although the objective itself has remained easy to understand: build SPARC and demonstrate high fusion gain.

Helion has a more awkward record.

Polaris was originally expected to demonstrate "net electricity" in 2024. The machine did begin operating around that period, but Helion did not announce the promised result and later changed the language around the target to "electricity from fusion."

The 2028 Microsoft deadline is harder to move quietly. Helion has already started Orion construction and secured important licenses, which shows that the company is spending real money against the timetable. The commercial pressure is useful.

CFS has chosen a slower dependency chain: finish SPARC, prove its performance, then move ARC toward construction and grid delivery. That introduces more calendar time but fewer simultaneous leaps.

So our forecast is straightforward. Helion has the earlier possible win. CFS has the schedule we would currently assign the higher probability of being achieved.

Q10Which fusion company looks easier to manufacture and scale, Helion or CFS?

Helion has the more attractive manufacturing model if its reactor works, although CFS is further ahead in manufacturing the critical hardware it needs right now.

CFS already operates a serious industrial magnet program. It moved from the famous 20-tesla demonstration magnet into production equipment, its own factory and full-size toroidal-field magnets for SPARC. This is one reason we take CFS's execution more seriously than a company that has only designed a reactor on paper.

The cost of that approach is complexity. ARC will be a large nuclear-scale infrastructure project with superconducting magnets, cryogenics, a vacuum vessel, a molten-salt blanket, heat-removal systems, tritium handling and conventional electricity-generation equipment.

Helion's long-term factory vision is more appealing. Its machines rely heavily on repeated electrical and pulsed-power components that can, in principle, move down a manufacturing learning curve. Helion is expanding in-house capacitor production and building manufacturing capacity around the hardware needed for future generators.

Direct energy recovery also reduces the amount of thermal conversion equipment Helion hopes to put around the fusion core.

If both companies eventually prove equally good fusion performance, we can imagine Helion scaling through factories faster than CFS scales through power-plant construction.

That remains a second-stage advantage. CFS already knows that its production magnets meet demanding specifications. Helion still needs the integrated reactor result that makes mass production worth discussing.

Q11Who has enough money to survive the fusion race, Helion or CFS?

CFS has the much stronger financial position now, with roughly $4 billion raised compared with about $1.5 billion for Helion.

The difference has become more important lately because CFS just added another $1 billion of equity. The company says its cumulative funding now represents roughly 30% of all capital raised by the private fusion industry.

Helion is hardly capital constrained by normal startup standards. Its latest $465 million round valued the company at $15.5 billion post-money and brought cumulative funding to $1.5 billion.

That valuation is revealing. Helion was valued at about $5.4 billion after its previous round, so investors nearly tripled the value of the company in roughly a year and a half. They are placing a very high price on Helion's chance of reaching commercial electricity first.

CFS declined to disclose a new valuation in its latest financing, so a clean valuation comparison is impossible.

The funding comparison is much easier. CFS has raised about 2.7 times as much capital as Helion.

Fusion can consume extraordinary amounts of money before commercial revenue appears. Both companies still face prototype work, factories, specialized materials, fuel systems, grid infrastructure and first-of-a-kind plant construction. A few major redesigns could add years and hundreds of millions of dollars.

CFS has considerably more room to absorb that kind of bad news.

Helion vs. CFS funding comparison

Q12Is CFS pulling ahead of the rest of private fusion too?

CFS currently has the strongest all-around position in private fusion, while Helion remains the most credible company trying to beat the tokamak route with a radically different architecture.

A two-company winner would mean little if another developer were setting the industry's pace.

The field has become crowded. TAE Technologies, Pacific Fusion, Zap Energy, Type One Energy, Tokamak Energy, Thea Energy, Proxima Fusion and several Chinese teams are all pursuing different combinations of confinement physics, fuels and reactor designs.

CFS still stands apart on capital. Its $4 billion total is in a different league from most fusion startups and, according to the company, accounts for around 30% of private fusion funding globally.

Its technical position is also unusual. The U.S. Department of Energy's latest fusion roadmap explicitly expects SPARC to become an important platform for the first magnetically confined fusion-gain experiments and, later, for studying burning plasmas at much higher gain.

Helion stands out for a different reason. It has pushed an alternative confinement concept much further toward an actual customer deadline than almost anyone expected a few years ago.

A successful Orion would therefore do more than move Helion ahead of CFS. It would challenge the industry's assumption that commercial fusion needed to follow the usual sequence of scientific breakeven machine, pilot plant and then commercial station.

For now, CFS sets the broader private-fusion benchmark. Helion has the clearest opportunity to upset it.

Q13What would Helion need to prove to overtake CFS?

Helion can overtake CFS surprisingly quickly if Polaris produces convincing electrical-output data and Orion then keeps moving toward repeatable operation.

The first result we want is very specific: Helion should show fusion energy being converted back into electricity through the machine's electrical system, with enough measurement detail to understand the energy balance.

A strong result there would connect several pieces that currently sit apart. Polaris's fusion performance would suddenly support the direct-electricity architecture. Orion construction would look much less speculative. The aggressive commercial timetable would also become easier to underwrite.

Repeatability comes next. A useful Helion generator must execute huge numbers of pulses while switches, capacitors, magnets, vacuum systems and plasma-control hardware behave reliably. A spectacular shot has little commercial value if the machine cannot repeat it.

We would also watch disclosure. Helion can keep proprietary engineering private and still release enough diagnostics for independent fusion scientists to judge confinement, energy recovery and scaling. Better external visibility would remove one of CFS's easiest advantages.

Finally, Orion needs to keep looking like a real power project: generator-building progress, hardware installation, commissioning work and a believable route to the grid.

If Helion delivers those pieces before CFS gets a strong SPARC result, we would change our answer.

Q14What would CFS need to prove to make its fusion lead convincing?

CFS can make its current lead much harder to challenge by getting a strong SPARC result and then moving quickly from plasma physics into ARC construction.

SPARC is the obvious test. CFS has published enough of its expectations that the result will be difficult to spin.

The machine was designed for fusion gain above Q=2 under conservative assumptions, with much higher performance projected under the nominal case. A weak result around the minimum threshold would still be important. Performance well into the expected high-gain regime would change the private-fusion landscape.

CFS has already built much of the credibility around SPARC before first plasma. The magnet technology works at full scale, the machine is close to complete, support systems are entering commissioning, and the DOE expects SPARC to play a major role in future U.S. burning-plasma research.

After that, the conversation shifts quickly to ARC.

CFS will need credible answers on tritium breeding, neutron-resistant materials, heat exhaust, maintenance and the economics of replacing highly stressed reactor components. The company's recent ARC papers are useful partly because they make those remaining problems visible.

We would then want to see speed. A successful SPARC followed by years of slow ARC development would give Helion and other competitors time to catch up.

A successful SPARC followed by rapid construction in Virginia would make CFS very difficult to dislodge.

Q15Who is winning now, Helion or CFS?

Commonwealth Fusion Systems is winning the fusion race today, although Helion is clearly ahead in the narrower race to put a commercial fusion plant on the grid first.

We give CFS the overall lead because the most important constraint in fusion is still proving that a power-plant concept survives contact with physics and engineering. CFS currently carries less uncertainty on that path.

Helion deserves the lead on several concrete measures. Polaris is already operating. Orion construction has begun. The company has moved remarkably far through regulation. Its architecture could eventually be easier to manufacture, and no serious fusion competitor has accepted a commercial deadline as aggressive as Helion's.

The problem is concentrated in one place, and it is a big place. Helion has yet to publish the electricity-from-fusion result that its current FAQ itself describes as one of the most important remaining steps. The FRC and D-He3 physics also attract more fundamental disagreement from outside researchers than CFS's high-field tokamak approach.

CFS currently offers a denser chain of evidence. The key magnet technology has been demonstrated and industrialized. SPARC is around 80% assembled. Its expected performance was published years before operation. ARC now has its own five-paper physics basis. Google and Eni have committed to buying power. The Virginia project is already moving through permitting and grid interconnection. CFS also has about 2.7 times Helion's cumulative funding.

We weight three criteria above everything else today: technical risk already removed, quality of external validation and financial capacity to finish the job. CFS leads all three.

The lead is still reversible. Fusion is approaching the stage where one experimental result can outweigh years of fundraising, partnerships and construction updates.

Helion changes the ranking by proving electricity recovery at Polaris and then showing that Orion can repeat the process reliably.

CFS strengthens the ranking by getting a strong SPARC fusion-gain result and moving quickly into ARC construction.

Until one of those events happens, we put CFS first.

Helion vs. CFS overall comparison