Helion Energy
Pulsed field-reversed-configuration fusion with D-He3 fuel; signed the world's first commercial fusion electricity PPA (Microsoft, 2023)
SectorsNuclear
Market Metrics
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
Updated at 2026-Q2
Funding History
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 |
Updated at 2026-Q2
Product Specifications
| 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 |
Updated at 2026-Q2
Partnerships & Investors
MicrosoftCustomer / PPA
May 2023 power purchase agreement: 50 MW delivery by 2028 with non-delivery penalties; world's first commercial fusion electricity contract.
NucorCustomer / PPA
Sep 2024 MoU for 500 MW fusion plant for Nucor steel-mill operations; non-binding development agreement.
Sam AltmanInvestor / Executive Chairman
Largest individual backer; led Series C; remains Executive Chairman during OpenAI CEO tenure.
BlackRockInvestor
Series E investor; one of few mainstream asset managers in deep fusion. Signals later-stage institutional acceptance.
SoftBankInvestor
Series E investor; ties to broader AI-power capacity thesis.
Mithril Capital + Capricorn + Founders FundLong-term Investors
Earliest backers (2014 onward); maintained position through all subsequent rounds.
Updated at 2026-Q2
Key Milestones
2013
Company Founded
David Kirtley, Chris Pihl, John Slough, George Votroubek spin Helion out of MSNW research
2018
Trenta Machine (6th-gen)
First device to reach commercial-relevant 100M C plasma temperature
Nov 2021
Series C at $3B
Sam Altman personally leads $500M round; becomes Executive Chairman
May 2023
Microsoft Fusion PPA
World's first commercial fusion electricity power purchase agreement: 50 MW delivery to Microsoft by 2028, with penalties for non-delivery
Jan 2025
Series F at $5.425B
$425M raise (Lightspeed, SoftBank, Nucor join); brings total over $1B
Mar 2024
Polaris Construction Start
7th-generation machine assembly begins at Everett, WA; targeted as first device to demonstrate net electricity production
2025
Polaris Pulse Testing
Initial pulse testing of Polaris underway; electricity demonstration timeline revised from original 2024 target
2025
Polaris Demonstrates DT Fusion
First privately developed fusion machine to show measurable deuterium-tritium fusion and 150M C plasma
Jun 2026
Series G at $15.5B
$465M led by Thrive Capital roughly triples the valuation; total raised over $1.5B
2028 (PPA target)
Microsoft 50 MW Delivery
Contractual delivery date for Microsoft PPA; the most consequential near-term fusion commercial milestone
Updated at 2026-Q2