The two primary thermal energy sources are geothermal and solar thermal, according to the Oregon Department of Energy. Geothermal energy uses heat from the earth. Solar thermal energy uses heat from the sun. As thermal energy is heat, the most efficient way to use it is in heating homes or businesses. However, it also generates electricity for other uses.
The U.S. Navy reports use of solar water heaters to provide the equivalent of the hot water used by 7,000 homes in 2009. It says the most efficient use of solar energy is lighting in homes and businesses, through installation of skylights, to reduce use of electricity for lights during the day. Thermal energy from the sun provides both passive and active solar heat in homes and businesses without depending on solar panels that convert this energy into electricity for other uses.
In Oregon, geothermal energy is the power source for two geothermal power plants responsible for 29 megawatts. The city of Klamath Falls provides geothermal energy as a direct supply of heat in a downtown district. In other Oregon counties, geothermal heat provides energy for swimming pools, resorts, industry and for heating buildings. Chevron operates several geothermal facilities around the world.