Published
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June 17, 2026
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By
Cody Good
Graphics & Design
- Athul Alexander
The following content is sponsored by Pulsar Helium
Helium-3: The Most Powerful Fuel by Energy Density
Key Takeaways
- As a potential fuel source in nuclear fusion, Helium-3 (~100M MJ/kg) is one of the most energy-dense fuels available.
- The next most energy dense fuel is Uranium-235 (4M MJ/kg) used in commercially proven nuclear fission, followed by Hydrogen (120 MJ/kg).
Helium-3 (He-3) is an extremely rare, non-radioactive helium isotope found in trace amounts on the Earth and on the Moon’s surface. As a potential fuel source in nuclear fusion, it’s one of the most energy-dense fuels available.
This graphic, created in partnership with Pulsar Helium, compares different fuel sources based on energy density. It’s part one of four in the Helium 3: From Theory to Opportunity series, delivering key He-3 insights for investors tracking deep tech, critical minerals, and advanced computing.
Helium-3 vs. Helium-4: What’s the Difference?
Helium-4 (He-4) is the gas commonly known to make balloons float, and makes up 99.999% of known helium on Earth. The difference from He-3 is at the atomic level where He-3 has one less neutron than He-4.
This difference causes unique changes in behavior that are valuable for quantum technologies and cryogenics. Most importantly, it’s critical to advanced fusion research as a potential fuel source.
Fuels Ranked by Energy Density
Gram-for-gram, He-3 is one of the most energy dense fuels around. Using practical reactor performance estimates as a theoretical fuel source, He-3’s energy density is 100M MJ/kg.
That makes it several orders of magnitude larger than the following more traditional fuel types.
| Fuel | Energy Density (MJ/kg) |
|---|---|
| Helium-3 (fusion) | 100,000,000 |
| Uranium-235 (fission) | 3,900,000 |
| Hydrogen | 120 |
| Natural Gas | 55 |
| Gasoline | 46 |
| Crude Oil | 44 |
| Biodiesel | 38 |
| Ethanol | 27 |
| Coal | 24 |
| Wood | 16 |
Source: U.S. DOE; I. Hore-Lacy, Nuclear Energy in the 21st Century; IAEA; NASA: Based on NASA’s He-3 fusion reaction energy (18.35 MeV per reaction), and IAEA reactor performance assumptions, the energy density of He-3 is about 100 million MJ/kg.
After He-3 is Uranium-235 (U-235), used in nuclear fission with an energy density of 4M MJ/kg followed by Hydrogen at 120 MJ/kg.
As a rough comparison, 1 kilogram of He-3 can generate as much energy as roughly 25 kilograms of U-235 or nearly 1 million kilograms of hydrogen.
Helium 3: From Theory to Opportunity
As global energy demand continues to climb, Helium-3 pairs potentially massive energy density with real-world strategic demand today.
For investors, it’s a high-upside emerging supply story to watch. Part two, the next graphic in the series, will deliver insights about the economics of He-3.
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