Helion, a nuclear fusion startup backed by Sam Altman, recently announced the completion of a new round of financing of US$465 million, raising the company's valuation to US$15.5 billion. The funds will be used to promote its first commercial nuclear fusion power station "Orion" project, with the goal of connecting fusion power to the grid by 2028 in accordance with the power supply agreement signed with Microsoft.
According to data disclosed by Helion, the company had previously completed US$425 million in financing in January 2025. The cumulative financing scale after this financing has reached US$1.5 billion, showing the capital market's continued bet on the commercialization prospects of nuclear fusion. This round is Series G financing, led by Thrive Capital. New shareholders include Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners and Bill Ford. Old shareholders Capricorn Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, Dustin Moskovitz’s Good Ventures Foundation, SoftBank Vision Fund 2 and a university’s endowment fund continue to invest.
The technical route taken by Helion is different from that of many peers. There are currently two main paths in the field of nuclear fusion: one is to use strong magnetic fields to confine high-temperature plasma, and the other is to use high-energy lasers to compress fuel to promote fusion reactions. Most companies plan to use the generated high-temperature steam to drive steam turbines to generate electricity. Helion also uses magnetic fields to compress fuel, but it does not intend to take the traditional route of "generating heat first and then converting it to steam". Instead, it attempts to "harvest" electrical energy directly from the magnets.
In Helion's design, when the plasma inside the reactor undergoes a fusion reaction, it will expand rapidly, pushing the external magnetic field to change, thereby generating a current in the magnet coil, similar to how an electric vehicle uses a "reverse drive" motor to achieve energy recovery braking and charge the battery. Helion uses deuterium and helium-3 as fuel. It is first heated and accelerated in a magnetic field, and then compressed to fusion conditions. The energy released by the reaction is then directly output in the form of induced current to greatly improve the overall energy efficiency.
If this concept can be realized, it will significantly improve the energy conversion efficiency of fusion power stations, but it has also caused doubts by some experts. Some physicists pointed out that, unlike many competitors, Helion rarely publishes papers on technical details in peer-reviewed journals, making it difficult for the academic community to comprehensively examine its theoretical basis. Therefore, some experts have reservations about its timetable and technical feasibility. Helion CEO David Kirtley responded that the company pays more attention to the actual operating results of the device rather than theoretical debates. He previously said, "We don't want to endlessly discuss fusion in theory, we just want to actually build the device."
Despite the controversy, Helion is not the only fusion company gaining traction in capital markets. In recent months, a number of fusion start-ups have announced that they have received large amounts of financing: for example, Focused Energy has just completed US$240 million in financing, focusing on laser-driven fusion solutions; Thea Energy has recently raised US$100 million, ranking among the top fusion companies with financing. In February this year, Inertia Energy came out of stealth and released US$450 million in Series A financing. Earlier, Type One Energy, backed by Bill Gates, announced that it was raising US$250 million in its Series B financing and had completed US$87 million in bridge funding.
Behind the continued influx of capital is the fact that the commercialization timeline of nuclear fusion is still long and full of uncertainty. Although some companies have successively announced the completion of key technology and engineering milestones in the past few months, believing that these achievements pave the way for the construction of commercial power plants in the future, most companies still predict that the first truly commercial-scale fusion power plant will likely not operate until after the middle of the next decade.
The reason why nuclear fusion is so popular is that once it is commercialized, it is expected to use a wide range of resources such as seawater to provide nearly "unlimited" stable power that is not affected by weather and day and night changes. For artificial intelligence companies that increasingly rely on high-performance computing power and large-scale data centers, cheap, stable and low-carbon power supply is extremely attractive. Once the LCOE of fusion power generation is significantly reduced, its potential impact will not only be limited to the AI industry, but may also have a disruptive impact on several other trillion-dollar energy market structures.
From the perspective of investment institutions, the time span of nuclear fusion projects far exceeds the usual exit cycle of traditional venture capital, but once it succeeds, the return space may also far exceed that of conventional technology projects. Helion’s huge financing and the power supply agreement it signed with Microsoft are regarded as another step towards nuclear fusion from the “laboratory stage” to “quasi-commercialization”, although there are still many technical and engineering challenges that need to be overcome before it can truly light up the power grid and stabilize power supply.