Helion, Sam Altman-Backed Fusion Startup, Raises $465M to Power Microsoft

Helion, the pioneering fusion startup backed by OpenAI CEO Sam Altman, has announced a significant milestone, securing $465 million in a new funding round. This latest infusion of capital elevates the company's valuation to an impressive $15.5 billion, underscoring the growing investor confidence in the future of fusion energy. The funding comes as Helion accelerates its efforts to complete Orion, its inaugural power plant, with an ambitious target to deploy fusion power to the grid as early as 2028, fulfilling the terms of its groundbreaking deal with Microsoft. This Series G round was spearheaded by Thrive Capital, attracting a diverse array of new investors including Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, and Bill Ford. Existing investors, such as Capricorn Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, Dustin Moskovitz through Good Ventures Foundation, SoftBank Vision Fund 2, and a university endowment fund, also participated. This latest round brings Helion's total capital raised to $1.5 billion, following a previous $425 million raise in January 2025, highlighting the substantial financial backing behind its innovative vision. Helion's approach to harnessing fusion power distinguishes it from many of its contemporaries. While many startups in the sector rely on magnets or lasers to create the superheated plasma necessary for fusion, and then use steam turbines to convert the intense heat into electricity, Helion employs a different strategy. It utilizes magnets to compress the fusion fuel, but critically, it intends to harvest electricity directly from the magnetic fields themselves. As fusion occurs within the reactor's plasma, it expands, pushing against the magnetic fields, a force that can be converted into electricity, akin to how an electric vehicle regenerates power during braking. This direct energy conversion method promises a dramatic improvement in the efficiency of a fusion power plant. However, this innovative approach has not been without its skeptics within the fusion community. Some experts express reservations, partly because Helion, unlike many of its competitors, does not frequently publish its findings in peer-reviewed journals, limiting the scientific scrutiny of its theoretical underpinnings. David Kirtley, Helion’s CEO, addresses this by emphasizing a practical, results-driven philosophy: “We don’t want to theorize about fusion. We just want to go build it.” The broader fusion sector has recently emerged as a magnet for investor interest, with Helion's funding round being part of a larger trend. Other companies like Focused Energy and Thea Energy recently announced new rounds of $240 million and $100 million, respectively. Inertia Energy emerged from stealth with a $450 million Series A in February, and Type One Energy is in the process of raising $250 million for its Series B. These investments are pouring in despite the inherently lengthy timelines associated with developing commercial fusion power. The allure of fusion power lies in its potential to deliver virtually limitless, always-on energy using readily available resources like seawater. This proposition is particularly attractive to AI-focused tech giants like Microsoft, which require vast and consistent energy supplies. Furthermore, successful commercialization of fusion could disrupt trillion-dollar energy markets by aggressively driving down costs. While the timelines for commercial operation—most companies predict the mid-next decade at the earliest—might be longer than typical venture capital horizons, the potential payoff in terms of global energy transformation is undeniably immense.