Ambient heat: Abundance
Limitless heat, limited by demand and electricity
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).Practically unlimited: the surface absorbs thousands of times more solar energy than humanity uses, so the limit is heat demand and electricity, not the resource. Heat pumps met about 10% of global space heating in 2021.
A flow: renewed continuouslyHow much there is
| Measure | Value | Compared with world energy use | Note |
|---|---|---|---|
| Solar energy absorbed at Earth's surface | about 83,000 TW (48% of 340 W/m2 over 5.1 x 10^14 m2, calculated)1 | about 4,400 times world primary energy use | This is the flow that keeps air, ground and surface water warm. |
| Global heat pump capacity installed (2021) | about 1,000 GW of heat output5 | IEA projects nearly 2,600 GW by 2030 in its Announced Pledges Scenario. | |
| Share of global space heating met by heat pumps (2021) | about 10%4 | ||
| Growth in ambient heat used in buildings, 2025-2030 (IEA forecast) | +1.3 EJ6 | about 0.2% of world primary energy use | About a quarter of projected growth in renewable heat in buildings; mainly China, then the EU and the US. |
| Heat pumps installed in 19 European countries (2024) | about 25.5 million units9 | The installed base avoids about 21 billion m3 of gas imports. |
The resource is the warmth of the environment itself, replenished continuously by sunlight, so tapping it does not deplete it on any practical scale. The binding constraints are elsewhere: the electricity to drive the pumps, the cost of equipment and how much low-temperature heat buildings and industry need.
No single global total of ambient heat captured is published, and the IEA notes that heat captured by industrial heat pumps is not yet counted at all. For scale, world primary energy use was 592 EJ in 2024 (Energy Institute Statistical Review 2025), while the IEA expects ambient heat in buildings to add 1.3 EJ between 2025 and 2030.
Sources
- Climate and Earth's Energy Budget NASA Earth Observatory, 2009
- The Future of Heat Pumps IEA, 2022
- The Future of Heat Pumps: Executive summary IEA, 2022
- Renewables 2025: Renewable heat IEA, 2025
- European Heat Pump Market and Statistics Report 2025: Executive summary European Heat Pump Association, 2025