The International Geothermal Association (IGA) has reported that 10,715 megawatts (MW) of geothermal power in 24 countries is online, which is expected to generate 67,246 GWh of electricity in 2010. This represents a 20% increase in online capacity since 2005. IGA projects growth to 18,500 MW by 2015, due to the projects presently under consideration, often in areas previously assumed to have little exploitable resource.

In 2010, the United States led the world in geothermal electricity production with 3,086 MW of installed capacity from 77 power plants. The largest group of geothermal power plants in the world is located at The Geysers, a geothermal field in California. The Philippines is the second highest producer, with 1,904 MW of capacity online. Geothermal power makes up approximately 18% of the country's electricity generation.

Country Capacity (MW)
Capacity (MW)
of national
Installed geothermal electric capacity
USA 2687 3086 0.3%
Philippines 1969.7 1904 27%
Indonesia 992 1197 3.7%
Mexico 953 958 3%
Italy 810.5 843 1.5%
New Zealand 471.6 628 10%
Iceland 421.2 575 30%
Japan 535.2 536 0.1%
Iran 250 250
El Salvador 204.2 204 25%
Kenya 128.8 167 11.2%
Costa Rica 162.5 166 14%
Nicaragua 87.4 88 10%
Russia 79 82
Turkey 38 82
Papua-New Guinea 56 56
Guatemala 53 52
Portugal 23 29
China 27.8 24
France 14.7 16
Ethiopia 7.3 7.3
Germany 8.4 6.6
Austria 1.1 1.4
Australia 0.2 1.1
Thailand 0.3 0.3
TOTAL 9,981.9 10,959.7

Geothermal electric plants were traditionally built exclusively on the edges of tectonic plates where high temperature geothermal resources are available near the surface. The development of binary cycle power plants and improvements in drilling and extraction technology enable enhanced geothermal systems over a much greater geographical range. Demonstration projects are operational in Landau-Pfalz, Germany, and Soultz-sous-ForĂȘts, France, while an earlier effort in Basel, Switzerland was shut down after it triggered earthquakes. Other demonstration projects are under construction in Australia, the United Kingdom, and the United States of America.

The thermal efficiency of geothermal electric plants is low, around 10-23%, because geothermal fluids do not reach the high temperatures of steam from boilers. The laws of thermodynamics limits the efficiency of heat engines in extracting useful energy. Exhaust heat is wasted, unless it can be used directly and locally, for example in greenhouses, timber mills, and district heating. System efficiency does not materially affect operational costs as it would for plants that use fuel, but it does affect return on the capital used to build the plant. In order to produce more energy than the pumps consume, electricity generation requires relatively hot fields and specialized heat cycles. Because geothermal power does not rely on variable sources of energy, unlike, for example, wind or solar, its capacity factor can be quite large – up to 96% has been demonstrated. The global average was 73% in 2005.