How close are we to fusion power?Can we bottle a star?
or, simply: Can we bottle a star?or, precisely: How close are we to fusion power?
Fusion has crossed scientific breakeven, but an economical power plant still requires a much harder engineering breakeven.We have made a tiny star flash in a laboratory; now we have to turn that flash into a dependable power station.
SPARC tokamak assembly underway - CFS began assembling SPARC in Devens, MA - cryostat base, both vacuum-vessel halves and the first high-temperature-superconducting magnet installed; facility ~75% complete. First plasma now targeted for 2026-27. Next up - SPARC targets Q > 10 (expected 2027).
State of playWhere nuclear fusion stands right now
The current stage, the honest metric, and the single threshold that gates the next stage. Each threshold is a falsifiable claim with a named next test.How far up the ladder we've climbed, the honest verdict, and the one thing blocking the next step.
We have made a tiny star flash in a laboratory; now we have to turn that flash into a dependable power station.Fusion has crossed scientific breakeven, but an economical power plant still requires a much harder engineering breakeven.
Make the whole power station pay back its energyEngineering breakeven Next test: SPARC targets Q>10, 2027
The thresholds that gate the next stageWhat has to happen next
Each threshold is a falsifiable claim with a named next test; the gap chart shows how far today's metric sits from the goal.Each row is one thing that has to be proven — and how far today's number is from the target.
The record behind the verdict
Major events set large; context events set small but never hidden. Everything below the TODAY rule is a schedule, not a result.
The theory takes shape
Fusion moved from a stellar explanation to a laboratory proposition. The basic reaction was understood before anyone had a machine capable of holding it.
The machines are built
The first generation of confinement machines turned equations into experiments. Tokamaks, large facilities, and sustained plasma became the field’s shared engineering language.
Chasing breakeven
Decades of larger machines narrowed the gap to useful gain, but each record exposed another layer between hot plasma and a power station.
From physics to power
NIF crossed scientific breakeven, while high-field magnets opened a smaller reactor path. The frontier is now engineering gain, maintainability, and affordable electricity.
Events outside the declared eras
Events outside the declared eras begins with arc - first electricity. The result established the next question for the field.
Why the meters read the way they do
The learning curves and comparisons that justify each threshold's percentage. Every series is measured, with the source event linked in the timeline above.
If the remaining tests pass
Downstream capabilities, drawn dashed because they depend on results not yet in.
Who is building it-and what the money saysCapital, institutions and the global race
The teams doing the work, where they are based, and whether the money points to real delivery or only a plan.Company finance, public programmes, institutional leadership and market evidence-kept separate from valuations, forecasts and announced capacity.
Fusion now has a well-funded private field alongside national laboratories and the seven-member ITER programme. The money is real, but commercial electricity is not: company plant dates, power-purchase agreements and national roadmaps remain targets until a system delivers net electricity reliably.
Who is building itCompanies, laboratories and programmes
Commonwealth Fusion Systems
USABuilding the high-field SPARC tokamak and developing the proposed ARC power plant.
Helion Energy
USADeveloping pulsed field-reversed-configuration machines with direct electrical energy recovery.
TAE Technologies
USADeveloping a beam-driven field-reversed configuration, ultimately targeting hydrogen-boron fuel.
| Player | Country | What they are doing | Funding | Named investors | Source |
|---|---|---|---|---|---|
| Commonwealth Fusion Systemscompany | USA | Building the high-field SPARC tokamak and developing the proposed ARC power plant. CFS described cumulative funding as nearly $3B; SPARC and ARC had not delivered electricity by the cutoff. | Series B2 · $863M · Aug 2025 | Breakthrough Energy Ventures · Google · NVentures · Eni · Temasek · Khosla Ventures | Source · cfs.energy |
| Helion Energycompany | USA | Developing pulsed field-reversed-configuration machines with direct electrical energy recovery. Helion says total invested exceeds $1B; its power-delivery schedule remains a company target. | Series F · $425M · Jan 2025 | Lightspeed Venture Partners · SoftBank Vision Fund 2 · Sam Altman · Nucor | Source · helionenergy.com |
| TAE Technologiescompany | USA | Developing a beam-driven field-reversed configuration, ultimately targeting hydrogen-boron fuel. TAE reported more than $1.3B private capital; its announced merger value is not funding raised. | Not disclosed | Google · Chevron Technology Ventures · Goldman Sachs · Sumitomo Corporation of Americas · NEA | Source · tae.com |
| ITER Organizationgovernment | International | Building a seven-member experimental tokamak to demonstrate burning-plasma feasibility, not commercial electricity. | Not disclosed | Not disclosed | Source · iter.org |
| National Ignition Facilitylab | USA | Runs laser-driven inertial-confinement experiments and has repeatedly achieved target-level ignition. Target gain excludes the much larger wall-plug energy used by the facility. | Not disclosed | Not disclosed | Source · lasers.llnl.gov |
Where every number comes from
3 sources — every figure on this page traces to one.