Geothermal power is power generated by geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation is currently used in 26 countries,   while geothermal heating is in use in 70 countries. As of , worldwide geothermal power capacity amounts to Geothermal power is considered to be a sustainable , renewable source of energy because the heat extraction is small compared with the Earth's heat content. It successfully lit four light bulbs.