Helion, Supported by Sam Altman, Raises $465M to Build a Power Plant for Microsoft.

Helion, the fusion startup backed by Sam Altman, announced on Thursday that it has raised $465 million in a recent funding round, valuing the company at $15.5 billion.

This funding comes as Helion accelerates plans to complete Orion, its first power plant. The startup intends to integrate fusion power into the grid by as early as 2028, dependent on meeting the conditions of its agreement with Microsoft.

In January 2025, Helion previously secured $425 million, bringing its total funding to $1.5 billion.

The latest Series G funding round was led by Thrive Capital, with contributions from various participants, including new investors such as Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, and Bill Ford. Existing backers like Capricorn Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, and Dustin Moskovitz via Good Ventures Foundation, SoftBank Vision Fund 2, among others, also took part.

Helion’s approach to fusion power sets it apart from many of its competitors. While some utilize magnets to contain the superheated plasma necessary for fusion, and others employ lasers to compress fusion fuel until a reaction occurs, most startups are planning to use steam turbines to convert the resulting heat into electricity.

Helion, on the other hand, aims to directly harness electricity from the magnets used to compress the fuel. When fusion occurs in the reactor’s plasma, it expands and pushes against the magnetic fields. This force can then be transformed into electricity, similar to how an electric vehicle can reverse its motors to generate braking force and recharge its battery.

This approach has the ability to greatly enhance the efficiency of a fusion power plant. However, some experts in the fusion field question its practicality, partly due to Helion’s inconsistent publications in peer-reviewed journals, which limits scrutiny of its theoretical principles. David Kirtley, the CEO of Helion, asserts that the eventual results of the company’s fusion technology will validate its effectiveness. “We don’t want to theorize about fusion,” he remarked last year. “We just want to go build it.”

Helion is not alone in attracting new investments; the fusion sector has recently gained investor interest. Focused Energy and Thea Energy both reported new funding rounds last week: Focused raised $240 million, while Thea obtained $100 million. In February, Inertia Energy emerged from stealth mode with a $450 million Series A funding, and the prior month, Type One Energy announced efforts to raise $250 million for its Series B.

Despite the long timelines associated with fusion, the flow of investments continues. While numerous companies have claimed milestones that will eventually lead to functional power plants, most anticipate that their first commercial-scale power plants will not be operational until at least the middle of the next decade.

The appeal of fusion lies in its potential for nearly limitless, around-the-clock energy derived from little more than seawater. This perspective is particularly alluring for AI-driven tech companies. Additionally, fusion power could disrupt existing trillion-dollar energy markets if companies manage to reduce costs. Although the timelines may extend beyond what VCs are accustomed to, the possible rewards could be significantly greater.