How fusion power works and the startups pursuing it

Fusion startups have raised more than 10 billion dollars in investment, with more than a dozen securing over 100 million dollars each. Large funding rounds have closed in the last year as investors respond to growing energy demand from data centers and advances in the technology. At its core, fusion power uses the energy from fusing atoms to generate electricity. Humans have achieved controlled nuclear fusion in experimental devices, with some producing more energy than needed to start the reaction. None have yet created a surplus sufficient for a commercial power plant. Startups are pursuing multiple technical approaches to reach that goal. Magnetic confinement relies on strong magnetic fields to contain plasma, the superheated particles central to fusion reactions. Commonwealth Fusion Systems is assembling magnets that generate 20 tesla fields, roughly 13 times stronger than a typical MRI machine, cooled to minus 253 degrees Celsius with liquid helium. The company is building a demonstration device called Sparc in Massachusetts with plans to activate it in late 2026. Successful operation could lead to construction of its commercial-scale plant, Arc, in Virginia starting in 2027 or 2028. Tokamaks and stellarators are the primary magnetic confinement designs. Tokamak Energy works on a spherical tokamak with its ST40 machine undergoing upgrades. Stellarators, which use twisted shapes based on plasma behavior modeling, include the Wendelstein 7-X device operating in Germany since 2015 and efforts by Proxima Fusion, Renaissance Fusion, Thea Energy, and Type One Energy. Inertial confinement compresses fuel pellets until atoms fuse, typically with converging laser pulses. The National Ignition Facility has achieved scientific breakeven in experiments where the reaction released more energy than it consumed. Nearly a dozen startups, including Focused Energy, Inertia Enterprises, Marvel Fusion, and Xcimer, are developing laser-based systems, while First Light Fusion explores pistons and Pacific Fusion electromagnetic pulses.