Geothermal energy is a type of energy stored in the form of heat beneath the surface of the solid earth. The use of geothermal energy depends on the temperature of the geothermal fluid. If this temperature is below 180º, then the most efficient use of the geothermal sources is in domestic heating or for heating the water. If the temperature of the geothermal fluid is 180º or above, then the energy associated with the geothermal fluid can be used for electricity generation. There is no geographical restriction to the exploitation of geothermal energy, as the source is present everywhere. However, some regions benefit from more favorable conditions that allow an earlier development of geothermal resources, under more economical conditions, using current available technology. As a consequence, the majority of the geothermal power plants in Europe are located in Italy, Iceland, and Turkey, where unusually high temperatures at comparatively limited depth dominate.