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Helion EnergyPulsed field-reversed-configuration fusion with D-He3 fuel; signed the world's first commercial fusion electricity PPA (Microsoft, 2023)
Microsoft Fusion PPA
50 MW by 2028
May 2023; world's first commercial fusion electricity PPA; non-delivery penalties (terms undisclosed)
Valuation (Jun 2026 Series G)
$15.5B
~3x from $5.425B (Jan 2025); led by Thrive Capital
Approach
Pulsed FRC + D-He3
Only major fusion developer pursuing direct-energy capture + aneutronic-leaning fuel cycle
Polaris Generation
7th machine
First private machine to show measurable DT fusion + 150M C; cumulative ~$1.9B invested
Total raised: ~$1.9B+ · Latest valuation: $15.5B
| Round | Date | Amount | Valuation | Key Investors |
|---|---|---|---|---|
| Pre-Seed / Y Combinator | 2014 | $1.5M | - | Y CombinatorMithril CapitalCapricorn Investment Group |
| Series A / B | 2015-2019 | $77M cumulative | - | Mithril CapitalCapricornDustin MoskovitzPeter Thiel |
| Series C | Nov 2021 | $500M | $3B | Sam Altman (lead, personal)Mithril CapitalDustin MoskovitzReid Hoffman+2 more |
| Series F | Jan 2025 | $425M | $5.425B | Sam Altman (personal)LightspeedSoftBank Vision Fund 2Mithril+2 more |
| Series G | Jun 2026 | $465M | $15.5B | Thrive Capital (lead)Lux CapitalPeak XV PartnersAlta Park Capital+2 more |
| System | Type | Status |
|---|---|---|
| Polaris (7th gen) | Pulsed FRC fusion machine with direct-energy capture | Under construction / commissioning at Everett, WA |
| Trenta (6th gen) | Prior-gen prototype achieving 100M C plasma | Decommissioned but published as reference |
| D-He3 Fuel Cycle | Aneutronic-leaning fuel approach (deuterium + helium-3) | R&D; targets reduced neutron flux + direct energy conversion |
| Direct Energy Capture | Skips steam turbine via inductive plasma deceleration | R&D; key differentiator from tokamak / NIF approaches |
| Microsoft Plant (planned) | 50 MW commercial fusion plant for Microsoft PPA | Site selection underway; target 2028 delivery |
May 2023 power purchase agreement: 50 MW delivery by 2028 with non-delivery penalties; world's first commercial fusion electricity contract.
Sep 2024 MoU for 500 MW fusion plant for Nucor steel-mill operations; non-binding development agreement.
Largest individual backer; led Series C; remains Executive Chairman during OpenAI CEO tenure.
Series E investor; one of few mainstream asset managers in deep fusion. Signals later-stage institutional acceptance.
Series E investor; ties to broader AI-power capacity thesis.
Earliest backers (2014 onward); maintained position through all subsequent rounds.
David Kirtley, Chris Pihl, John Slough, George Votroubek spin Helion out of MSNW research
First device to reach commercial-relevant 100M C plasma temperature
Sam Altman personally leads $500M round; becomes Executive Chairman
World's first commercial fusion electricity power purchase agreement: 50 MW delivery to Microsoft by 2028, with penalties for non-delivery
$425M raise (Lightspeed, SoftBank, Nucor join); brings total over $1B
7th-generation machine assembly begins at Everett, WA; targeted as first device to demonstrate net electricity production
Initial pulse testing of Polaris underway; electricity demonstration timeline revised from original 2024 target
First privately developed fusion machine to show measurable deuterium-tritium fusion and 150M C plasma
$465M led by Thrive Capital roughly triples the valuation; total raised over $1.5B
Contractual delivery date for Microsoft PPA; the most consequential near-term fusion commercial milestone
Developer of a pulsed field-reversed configuration (FRC) reactor using D-He3 fuel. Signed the world's first commercial fusion PPA with Microsoft in May 2023 (50 MW, 2028 target). Raised approximately $1B+ across multiple rounds. Polaris machine electricity demonstration revised from 2024. Helion Energy was founded in 2013, is headquartered in Everett, WA and employs ~250.
Helion Energy has raised ~$1.9B+ in total at a $15.5B valuation, based on the funding rounds Sterling tracks.
Sterling groups Helion Energy in the Nuclear sector, alongside Commonwealth Fusion Systems (private), TAE Technologies (private), Tokamak Energy (private), Pacific Fusion (private) and General Fusion (private).
If you are researching Helion Energy, also look at Commonwealth Fusion Systems (private), TAE Technologies (private) and Tokamak Energy (private). You can browse the full Nuclear sector on Sterling.
