Helion Energy’s CEO David Kirtley and CFO Pragav Jain announced today that the company’s Series G round has reached final close at $500 million, upsized from its initial announcement after investor demand ran higher than the company wanted to take.
That final figure has not yet been independently confirmed by wire services or business press and is currently sourced to the executives’ own statements; readers should check Helion’s newsroom for confirmation.
For context, Helion Energy, the Everett, Washington fusion company, first announced this Series G round on June 4, 2026, at $465 million.
Thrive Capital led it. That initial figure valued Helion at $15.5 billion post-money and pushed its total capital raised to more than $1.5 billion.
The jump in valuation
Helion closed its Series F in January 2025 at a $5.4 billion valuation.
Eighteen months later, that number is $15.5 billion, a roughly threefold increase.
For a company that hasn’t yet delivered net electricity from fusion to any customer, that’s a steep repricing.
This is an ongoing trend for other fusion companies in the space too, with Commonwealth Fusion Systems raising an additional $1 Billion, bringing its total amount raised till date to $4 Billion.
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Who invested
Thrive Capital led the round. Other participants named in company and press materials include Lux Capital, Peak XV Partners, Lightspeed Venture Partners, SoftBank Vision Fund 2, Alta Park Capital, Anti Fund, BoxGroup, and Ford Motor Company executive chairman Bill Ford, investing personally.
Helion’s reporting also describes participation from crossover investors, sovereign wealth funds, and pension capital, a mix that isn’t typical for a company still years from commercial operation.
Sam Altman has been Helion’s executive chairman and a major investor since 2015.
He remains involved, and OpenAI’s own growing electricity needs give that involvement an obvious business rationale beyond personal conviction.
What justified the raise
Helion’s seventh-generation prototype, Polaris, became the first privately funded fusion machine to run on a deuterium-tritium fuel mix and produce measurable fusion.
It also reached plasma temperatures above 150 million degrees Celsius, a new company record.
What the money is for
Kirtley has said the company’s main constraint is shifting from proving the physics to building and repeating it at commercial scale.
Based on Helion’s statements and Puget Sound business coverage, the proceeds go toward three things:
1. Manufacturing. Expanding U.S. manufacturing capacity, including the Omega capacitor facility in Everett.
2. Orion. Building what Helion calls the world’s first commercial fusion power plant, under construction in Malaga, Washington.
3. Contracts. A 2023 power purchase agreement with Microsoft for at least 50 megawatts of fusion electricity by 2028, reportedly with financial penalties if Helion misses the date, and a separate agreement with Nucor to develop a 500-megawatt plant.
What to watch
No fusion company, Helion included, has yet built a plant that produces more electricity than it consumes at commercial scale.
Helion’s approach uses a field-reversed configuration with direct energy recovery, a different design path than the tokamak approach used by Commonwealth Fusion Systems.
It has produced verifiable milestones, but 2028 delivery dates in fusion have slipped before, industry-wide.
The investor list is also worth reading as a bet on AI power demand as much as fusion physics.
Altman’s dual role at OpenAI and Helion, and reported talks between the two companies about future power purchases, ties this round directly to how much electricity AI data centers end up needing.
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