Helion Energy Inc., a fusion power startup, has raised $465 million in a Series G funding round led by Thrive Capital. The company’s valuation now stands at $15.5 billion, up from $5.2 billion after its last funding in January 2025. This marks one of the largest single-round valuations for a clean energy firm in recent years. The funding includes participation from SoftBank Vision Fund 2, Lightspeed, and over half a dozen other investors.
The company is working on a fusion reactor named Polaris, designed to generate electricity by fusing atomic nuclei. Fusion occurs when two atomic nuclei merge, creating a slightly lighter nucleus. The mass difference is converted into energy, a process that has long been a scientific goal but remains technically challenging. Helion claims its reactor design will overcome these hurdles.
Related: Healthcare AI trust hinges on data foundations
Polaris is a cylindrical structure that uses a fuel called D-He-3. The process begins by inserting this fuel into the ends of the cylinder. The reactor turns the fuel into plasma, a charged mixture of electrons and atoms. Magnetic fields then compress the plasma into a donut-like shape. Once ready, the plasma donuts are accelerated toward each other at 100 million miles per hour.
The collision compresses the fuel further, and a magnetic field increases pressure and heat inside the reactor. This creates conditions for atomic nuclei to fuse. Changes in the magnetic field caused by the reaction generate an electric current. The system avoids continuous heating, relying instead on discrete fusion events.
Related: A.I. Revolutionizes Cybersecurity: The Future of Data Protection
The radiation from Polaris consists of protons, which are easier to manage than neutrons produced by other reactors. This reduces the need for shielding equipment, cooling towers, and turbines. Helion says its design cuts costs compared to traditional fusion systems. The company plans to use the funding to expand manufacturing and speed up commercialization.
The company started construction on its first commercial fusion power plant in Malaga, Washington, last year. The facility, expected to generate 50 megawatts when operational in 2028, is part of a broader effort to scale fusion energy. The company aims to demonstrate that discrete fusion events can power plants without requiring continuous heating.
Related: 7 Surprising Facts About Software You Probably Didn’t Know
The fuel used in Polaris, D-He-3, requires careful manufacturing. Helion says it will produce the necessary components in-house. The process involves shaping plasma into donuts, merging them, and repeating the cycle. This approach avoids the need for fusion ignition, a phenomenon that other reactors rely on to sustain their own heating.
Experts in the field have noted the challenges of producing helium-3 at scale. Helion’s strategy hinges on its ability to manage these challenges while keeping costs low. The company’s focus on reducing shielding and cooling requirements may give it an edge over competitors. However, the path to commercial viability remains uncertain.
