The high concentration of volcanoes in Iceland is an advantage in the production of geothermal energy, the heating and production of electricity using the heat of the earth. For example, geothermal energy is used to keep roads in the cities of Reykjavik and Akureyri free from snow and ice. In addition, five major geothermal power plants in Iceland produce approximately one-quarter of the nation's energy. Geothermal energy is also used to heat and produce hot water for about 90% of all buildings in Iceland.