For decades, humanity has pursued the dream of harnessing stellar energy to generate electricity on Earth, yet this aspiration often feels perpetually just out of reach.
Today, a wave of startups is rapidly advancing, working towards creating fusion reactors that could potentially supply power to the grid.
Fusion startups have attracted over $10 billion in investments, with more than a dozen companies securing at least $100 million each. The past year has seen significant funding rounds, spurred by increasing energy demands from data centers and the fact that fusion technology is edging closer to feasibility.
At its core, fusion energy aims to exploit the heat generated from fusing atomic nuclei to produce electricity. While the concept of atomic fusion has been understood for decades, from its applications in hydrogen bombs to controlled fusion in laboratories, none have yet achieved a surplus energy output sufficient for practical power generation.
To overcome this hurdle, various fusion startups are experimenting with different methodologies. Experts remain divided on which approaches hold the most promise, reminding us that the fusion industry is still in its nascent stages, making predictions uncertain.
Below is an overview of the primary methodologies being explored in the quest for successful fusion power.
Magnetic Confinement
Magnetic confinement is among the leading techniques for achieving fusion, employing potent magnetic fields to contain plasma—the superheated gas of particles that forms the core of fusion reactions.
These magnets are exceptionally powerful. For instance, Commonwealth Fusion Systems (CFS) is developing magnets capable of generating 20 tesla magnetic fields, which is approximately 13 times stronger than a standard MRI machine. To manage the electricity requirements, these magnets are crafted from high-temperature superconductors, which need to be cooled to –253˚ C (–423˚ F) using liquid helium.
CFS is currently constructing a demonstration device called Sparc in Massachusetts, with plans to activate it by late 2026. Should the project succeed, they intend to break ground on Arc, a commercial-scale power plant, in Virginia in 2027 or 2028.
There are two primary types of fusion devices that utilize magnetic confinement: tokamaks and stellarators. Tokamaks, first proposed by Soviet scientists in the 1950s, come in two forms—a doughnut shape with a D-profile and a spherical configuration with a central opening. Noteworthy experimental tokamaks include JET, operational in the UK from 1983 to 2023, and ITER, which is expected to start operations in France by the late 2030s.
Based in the UK, Tokamak Energy is advancing a spherical tokamak design, currently upgrading its ST40 experimental machine. Stellarators function similarly but feature twisted geometries. Instead of forcing plasma into a specific shape, they are designed to accommodate plasma behavior through tailored magnetic fields. The Wendelstein 7-X, operational in Germany since 2015 and managed by the Max Planck Institute for Plasma Physics, exemplifies a large stellarator. Numerous startups, including Proxima Fusion, Renaissance Fusion, Thea Energy, and Type One Energy, are also pursuing stellarator designs.
Inertial Confinement
Inertial confinement is another major approach to fusion, focusing on compressing fuel pellets until the constituent atoms undergo fusion.
Typically, this method utilizes laser beams that simultaneously converge on a fuel pellet from multiple directions. The ensemble of laser pulses compresses the pellet, igniting fusion.
In fact, inertial confinement has been the only approach to achieve what is known as scientific breakeven, where the reaction releases more energy than it consumes. These landmark experiments were conducted at the National Ignition Facility (NIF) in California. It is important to note that the measures of scientific breakeven do not account for the electricity needed to power the facility itself.
Nevertheless, a variety of startups are optimistic about inertial confinement and are developing reactors based on this technology. Notable companies in this space include Focused Energy, Inertia Enterprises, Marvel Fusion, and Xcimer, all leveraging lasers in their designs. Meanwhile, First Light Fusion employs pistons, and Pacific Fusion is utilizing electromagnetic pulses instead of lasers.
Emerging Approaches
While magnetic and inertial confinement are the two primary methodologies gaining traction, they are not the only avenues being explored. Future developments in alternative fusion designs—including magnetized target fusion, magnetic-electrostatic confinement, and muon-catalyzed fusion—are on the horizon and warrant further exploration.