The U.S. uses a variety of primary energy sources including petroleum, coal, natural gas, nuclear, hydropower, geothermal, wind, solar and biomass. These energy sources can be classified as renewable and nonrenewable. Renewable energy sources are sources that have the inability to be depleted. Solar, hydropower, wind, geothermal and biomass are all examples. Nonrenewable energy sources will eventually run dry. These sources include the fossil fuels; oil, coal and natural gas.