Helion Energy company profile: valuation, funding & revenue

This Helion Energy company profile covers the company's valuation, revenue, funding rounds, investors and history. Helion Energy works in climate and energy, with a focus on fusion power. It was founded in 2013 and is headquartered in Everett, Washington, United States. Its latest valuation on record is US$15.5 billion (post-money) (June 2026). Every figure links to a public source, and anything the company hasn't disclosed is marked as such.

Revenue

Funding history

Helion Energy timeline

Key dates from the sources on this page, oldest first. Metric snapshots are listed after the funding events.

• 2013 — Helion Energy is founded in Everett by David Kirtley (CEO), John Slough, Chris Pihl and George Votroubek.
• Nov 2021 — Series E: US$500M, valuing the company at About US$3B. Investors: Sam Altman (lead), Mithril Capital, Capricorn.
• Jan 2025 — Series F: US$425M, valuing the company at About US$5.4B. Investors: Lightspeed Venture Partners, SoftBank Vision Fund 2, a university endowment; Sam Altman, Mithril Capital, Nucor.
• Jun 2026 — Series G: US$465M, valuing the company at US$15.5B. Investors: Thrive Capital (lead); Lux, Peak XV, BoxGroup, Lightspeed, SoftBank Vision Fund 2.
• January 2025 — Total funding: More than US$1 billion.

Investors

Overview

Helion Energy is trying to build the world's first commercial fusion power plant. Fusion, the process that powers the sun, joins light atoms together and releases enormous energy with no carbon emissions and far less long-lived radioactive waste than today's nuclear fission plants. Scientists have pursued fusion power for more than 70 years. Helion stands out because it has signed an agreement to sell electricity to Microsoft from a plant it aims to bring online in 2028, an extraordinarily ambitious timeline that has made it one of the most closely watched energy companies in the world.

David Kirtley, the CEO, founded Helion in 2013 with John Slough, Chris Pihl and George Votroubek, who had worked together on fusion research, including at the University of Washington and a company called MSNW. Helion is based in Everett, Washington, north of Seattle. Sam Altman, the CEO of OpenAI, has been its largest individual investor and chairman of the board.

Helion's approach

Most fusion efforts, including large government projects such as ITER and companies such as Commonwealth Fusion Systems, use tokamaks: doughnut-shaped machines that hold hot plasma steady with powerful magnets. Helion uses a different design called pulsed magneto-inertial fusion. It forms two rings of plasma, called field-reversed configurations, at opposite ends of a long machine, fires them towards each other at very high speed, merges them in the middle and compresses them with magnets until they're hot enough to fuse. The process repeats in pulses.

Helion's biggest claimed advantage is how it captures energy. Instead of using fusion heat to boil water and drive turbines, as conventional power plants do, Helion aims to recover electricity directly: as the fusing plasma expands, it pushes back on the magnetic field, inducing an electric current that can be captured. If it works at scale, this could be more efficient and simpler than steam-based systems. Helion also plans to use a fuel mix of deuterium and helium-3, which produces fewer high-energy neutrons than the more common deuterium-tritium fuel, although it requires much higher temperatures.

Machines and milestones

• Trenta: Helion's sixth prototype, which the company said reached plasma temperatures of 100 million degrees Celsius.
• Polaris: its seventh machine, designed to demonstrate the production of electricity from fusion, which would be a world first for a fusion device.
• Orion: the planned commercial plant in Malaga, Washington, where construction began in 2025, intended to supply power to Microsoft.

The Microsoft deal

In 2023 Helion signed a power purchase agreement with Microsoft to provide at least 50 megawatts of electricity from 2028, with financial penalties if it fails to deliver. Constellation Energy is the power marketer. Many fusion scientists consider 2028 extremely optimistic, but the agreement gives Helion a concrete customer and target. It also reflects how technology companies, facing soaring electricity demand from AI data centres, are signing deals with advanced nuclear and fusion developers.

Funding

Helion raised a US$500 million Series E in 2021, led by Sam Altman, at about US$3 billion, with commitments for up to US$1.7 billion more tied to milestones. In January 2025 it raised a US$425 million Series F at about US$5.4 billion, with new investors Lightspeed Venture Partners, SoftBank Vision Fund 2 and a university endowment, and existing backers including Altman, Mithril Capital and steelmaker Nucor. Total funding exceeds US$1 billion. Nucor has also agreed to work with Helion on a 500-megawatt plant for one of its steel mills.

Helion Energy at a glance

Helion Energy is a fusion company founded in 2013 in Everett, Washington, led by David Kirtley and chaired by Sam Altman. It uses pulsed magneto-inertial fusion with direct electricity recovery. It has a deal to supply Microsoft from 2028 and raised a US$425 million Series F at about US$5.4 billion in January 2025.

Why fusion is so hard

To fuse, atomic nuclei must overcome their natural repulsion, which requires temperatures of tens to hundreds of millions of degrees and enough density and confinement time for reactions to occur. Holding plasma that hot without it touching the walls of the machine and cooling down is extremely difficult. Then a plant must produce more electricity than it consumes, operate reliably for years, withstand the stress of continuous operation and do all of this at a competitive cost. No fusion device has yet produced net electricity. The US National Ignition Facility achieved "ignition", more fusion energy out than laser energy in, in 2022, but that counted only the laser energy delivered, not the far larger amount used to power the lasers.

The fusion industry

Private fusion companies have raised billions of dollars in recent years. Major players include Commonwealth Fusion Systems, TAE Technologies, General Fusion, Tokamak Energy, Zap Energy and Pacific Fusion, each pursuing different designs. Governments are also investing, and regulators in the US and UK have decided to regulate fusion more like particle accelerators than fission reactors, which could make licensing simpler. Our guide to climate tech startups covers fusion alongside other clean energy technologies.

Questions to ask about fusion claims

• Has the machine demonstrated net energy gain, and how is that measured?
• How will fuel be sourced, especially scarce helium-3?
• What is the expected cost per megawatt-hour compared with other clean power?
• How long can components last under repeated pulses?

Latest developments (October 2026)

Helion raised a US$465 million Series G on 4 June 2026 at a US$15.5 billion post-money valuation, led by Thrive Capital, bringing total funding to about US$1.5 billion, according to Helion. New investors included Lux Capital, Peak XV Partners and BoxGroup, with Lightspeed, SoftBank Vision Fund 2 and Mithril returning. Reuters noted the valuation nearly tripled from January 2025, according to Kitco. Helion is building its Orion plant in Washington state to supply Microsoft. This supersedes the 2025 valuation described earlier on this page. See our nuclear and fusion guide.

What to watch

Watch for results from Polaris, especially any demonstration of electricity production, progress on the Orion plant, regulatory approvals, new funding and whether the 2028 Microsoft timeline holds.

Takeaways

Utilities and large energy buyers can follow Helion as a potential future source of firm clean power. Founders can learn from its use of customer contracts to anchor ambitious timelines. Investors should recognise fusion's enormous upside alongside very high technical risk.

Sources

Every figure on this page comes from the public sources below. Where sources disagreed, we used the company's own announcement or a primary news report. Private-company data changes; check the date beside each figure.

1. Helion
2. CleanTech Alliance (GeekWire)
3. Commercial Fusion