Geothermal power plants produce power using heat from underground reservoirs of hot water or steam heated by the surrounding rock  In the limited areas of the world where such underground hot water and steam can currently be reached by drilling, geothermal power plants produce power more economically than conventional, fossil fuel power plants
However, advocates contend that in the near future economical power from geothermal power plants will be available in most areas
The high start-up costs of geothermal power plants discourages their construction even in locations where they are more economical than conventional power plants in the long run.