Geothermal power plants: Efficiency
Low efficiency, but almost never switched off
What this tab covers How much of the energy available is actually captured or extracted, in per cent: theoretical limits, laboratory records, typical new equipment and in-service averages, each with exactly what is being measured.Geothermal plants turn only about 1-21% of the heat in the produced fluid into electricity, around 12% on average, because the fluid is far cooler than the steam in a fossil plant. They make up for this with very high capacity factors, about 85% on average for plants built in 2025.
Chart: Efficiency ranges
Theoretical limit In service RecordEfficiency by measure
| Measure | Range | Type | What is measured |
|---|---|---|---|
| Carnot limit, 250 °C fluid, 25 °C surroundings | 43%1 | Theoretical limit | Theoretical maximum heat-to-work efficiency, 1 - 298 K / 523 K (calculated) |
| Geothermal power plants worldwide (94 plants of all types) | 1 to 21%1 | In service | Heat in produced fluid to net electricity (conversion efficiency) |
| World average | 12%1 | In service | Same basis, average of the 94 plants |
| Best plant reviewed (Darajat, Indonesia, dry steam) | 21%1 | Record | Same basis; vapour-dominated fields do best |
| Binary plants on the coolest fluids | 1%1 | In service | Same basis, fluid enthalpy as low as 306 kJ/kg |
| Capacity factor, new projects | 77 to 88%213 | In service | Global average for projects commissioned each year: 77-88% over 2010-2024 (2024, IRENA); 85% in 2025 |
Where the energy is lost
| Step | Loss |
|---|---|
| Heat not converted: rejected in the condenser and cooling towers or returned in warm reinjected fluid | about 79-99% of the heat in the produced fluid, 88% on average (calculated)1 |
Efficiency rises with the enthalpy (heat content) of the produced fluid, which is why dry steam and flash plants on hot fields do best and binary plants on cool water worst. Zarrouk and Moon's review of 94 plants found the estimates for binary plants least certain, because air-cooled condensers are sensitive to local and seasonal air temperature. Because the heat itself is free, developers optimise for electricity per well rather than for thermal efficiency.