Renewable energy is sustainable as it is obtained from sources that are inexhaustible (unlike fossil fuels). Renewable energy sources include wind, solar, biomass, geothermal and hydro, all of which occur naturally. It is clean energy and non-polluting. Many forms do not emit any greenhouse gases or toxic waste in the process of producing electricity. It is a sustainable energy source that can be relied on for the long-term. Renewable energy is cost-effective and efficient.