On Tuesday a fusion energy start-up announced that it has applied to join a U.S. power grid—a first that could one day see households and businesses powered by nuclear fusion.
Commonwealth Fusion Systems is looking to join a power grid that is operated by PJM Interconnection and provides 182,000 megawatts of power to more than 67 million people living in 13 states and Washington, D.C. But technical hurdles to bringing fusion online remain—one major obstacle is actually producing a stable fusion reaction that generates more energy than it consumes.
The application process requires a potential energy provider to provide extensive technical information to the grid operator, including descriptions of the planned fuel type. In Commonwealth’s case, the company is developing a tokamak reactor design that uses high-powered lasers and powerful magnetic fields to combine two isotopes of hydrogen—deuterium and tritium—in a process that mimics the nuclear reactions in the sun. The promise of the device is that a fusion reaction could feasibly generate limitless clean energy. That energy, in the form of heat, is used to boil water into steam, which then pushes a turbine to produce electricity.
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Much of that process remains theoretical, however, because physicists have yet to prove that fusion can work as a large-scale power source. Recent results from Germany’s Wendelstein 7-X demonstrated it could contain superheated plasma for 43 seconds. And its rival, the Joint European Torus, was apparently able to accomplish that feat for a full minute before its reactor was retired in 2023. While such capabilities are impressive, there is still a long way to go before a fusion device could be connected to a grid. Commonwealth plans to open its first power plant, called ARC (for “affordable, robust, compact”), in Virginia in the early 2030s. And the company aims to demonstrate an initial model, called SPARC (for “smallest possible ARC”), in 2027.
Commonwealth has demonstrated some success: The company’s toroidal field magnet technology was validated by the Department of Energy in September 2025. The superconducting magnets generate the magnetic field that is used to contain the high-temperature plasma generated by a fusion reaction. But Commonwealth has yet to test the full system.
Commonwealth co-founder and CEO Bob Mumgaard said in a statement that the company is committed “to delivering the benefits of fusion, and enabling a future with abundant, secure energy, [which] means that we’re not just proving fusion physics works—we’re showing exactly how fusion power plant watts get from our machine to the customer, working with the grid and a utility.”
“By becoming the first fusion energy developer to enter a major grid operator’s interconnection queue, we’re demonstrating that when you’re serious about building a power plant in the early 2030s, you act now,” he said. “This is execution.”
Commonwealth’s application will likely take years to be approved; the company will navigate a complex process that will include several impact studies and other analyses, as well as reviews of the its capabilities, readiness, safety controls and other compliance.
PJM Interconnection did not immediately reply to a request for comment.
