Water cycle: Abundance
How much of the world's rain could become power
How much of the world's rain could become power 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).The gross theoretical hydropower potential is about 52 to 128 PWh a year (a third to four fifths of world primary energy), of which about 16 to 26 PWh is technically or practically exploitable. Hydropower produced about 4,400 to 4,600 TWh in 2024, roughly 2.7% of world primary energy.
A flow: renewed continuouslyHow much there is
| Measure | Value | Compared with world energy use | Note |
|---|---|---|---|
| Solar power driving evaporation | about 43,000 TW2 | about 2,300 times world primary energy use | Calculated as about 85 W/m2 times the Earth's surface area; almost all returns to the atmosphere as heat. |
| Gross theoretical hydropower potential (Zhou et al.) | about 128 PWh per year4 | about 0.78 times world primary energy use (461 EJ) | Upper published estimate of the gross potential; economic 21 and exploitable 16 PWh in the same study. |
| Gross theoretical hydropower potential (Hoes et al.) | about 52 PWh per year5 | about 0.32 times world primary energy use (187 EJ) | Spread over 11.8 million candidate locations; the gap with Zhou reflects different runoff data, river networks and resolution. |
| Technical potential | about 26 PWh per year4 | about 0.16 times world primary energy use (94 EJ of electricity) | Zhou et al. 2015; economic 21 PWh, exploitable 16 PWh after protected areas and other limits. |
| Hydropower generated in 2024 | 4,416 to 4,578 TWh6 | about 2.7 to 2.8% of world primary energy use (15.9 to 16.5 EJ) | Ember gives 4,416 TWh (up 4.3%; 14.3% of world electricity); IHA and REN21 give about 4,578 TWh (up 10%). The sources use different data and estimation methods. |
| World primary energy use (baseline) | 592 EJ in 20241 | 1 | Total energy supply, Energy Institute. |
Of the roughly 43,000 TW of solar power used to evaporate water, less than 0.05% (about 15 TW at the higher estimate of 128 PWh a year) survives as potential energy of water on land. Hydropower is therefore a large resource in electricity terms but a small one compared with world energy use.
Hoes and colleagues put the gross potential at 52 PWh a year, 33% of global energy needs, against present hydropower output of about 3%. Today's 4.4 to 4.6 PWh is already about 28% of Zhou's exploitable 16 PWh, so the remaining room is real but limited. Africa has harnessed only about 11% of more than 600 GW of potential.
Sources
- Energy Institute Statistical Review of World Energy 2025 (74th edition) Energy Institute (with KPMG and Kearney), 2025
- The global energy balance from a surface perspective (Wild et al., Climate Dynamics 40, 3107-3134) Springer / RERO DOC, 2013
- A comprehensive view of global potential for hydro-generated electricity (Zhou et al., Energy and Environmental Science 8, 2622-2633) Royal Society of Chemistry, 2015
- Systematic high-resolution assessment of global hydropower potential (Hoes et al., PLOS ONE 12(2)) Utrecht University Research Portal, 2017
- Global Electricity Review 2025: Global electricity source trends Ember, 2025