Fusion fuels: Abundance
Fuel for millions of years, but no working plant
What this tab covers How much of this energy there is: the natural flow or stock, the share that could be harnessed, and how much is used today, compared with world primary energy use (592 EJ in 2024).Deuterium in the oceans and lithium on land and in seawater could in principle supply world energy for millions of years. Today's supply of tritium is only a few tens of kilograms, and no fusion plant yet produces net electricity.
A stock: finite on human time scalesHow much there is
| Measure | Value | Compared with world energy use | Note |
|---|---|---|---|
| Deuterium in seawater | 33 g per m34 | effectively unlimited: no realistic demand would deplete the oceans | IAEA: deuterium can be extracted inexpensively from seawater |
| World lithium reserves | about 37 million tonnes Li5 | ITER estimates land lithium could supply fusion plants for more than 1,000 years | Measured and indicated resources about 150 million tonnes |
| Lithium in seawater | enough for about 6 million years years of world energy needs4 | about 6 million years at current world energy demand (ITER estimate) | Extraction from seawater not yet commercial |
| World tritium inventory | about 20-30 kg6 | a 1,000 MW plant would need about 125 kg a year, so plants must breed their own | ITER puts it at about 20 kg and Pearson (IAEA, 2022) at about 30 kg, mostly held in Canada; CANDU heavy-water reactors make about 2 kg a year and the stockpile decays |
| Helium-3 on the Moon (potential resource base) | about 1,000,000 tonnes7 | large in theory, but would require mining lunar soil at scale | About 25 t of helium-3 per km2 of high-titanium regolith mined to 3 m depth |
| Largest fusion energy released by a tokamak | 69 MJ (in 5 seconds, from 0.2 mg of fuel)8 | negligible: no net energy delivered to a grid | JET, UK, final deuterium-tritium campaign, 2023 |
On paper fusion fuel is the largest energy resource on Earth. The binding constraint is not fuel but machines: no fusion device has yet delivered net electricity, and the record laser shot at the US National Ignition Facility (8.6 MJ of fusion energy from 2.08 MJ of laser light in April 2025) ignores the far larger electricity drawn by the lasers.
In the near term the scarce fuel is tritium. The world's civilian stock of a few tens of kilograms would be consumed in a few months by a single gigawatt plant, so any commercial reactor must breed more tritium than it burns, using lithium enriched in lithium-6, which makes up only about 7.4% of natural lithium.
Sources
- Fusion fuels ITER Organization, 2024
- Mineral Commodity Summaries 2026: Lithium US Geological Survey, 2026
- Resource availability and supply for fusion (R.J. Pearson, IAEA technical meeting) International Atomic Energy Agency, 2022
- Lunar helium-3 and fusion power (NASA Conference Publication 10018) NASA Technical Reports Server, 1988
- New world record set in JET's final fusion experiments World Nuclear News, 2024