In the energy industry, these terms refer to source energy which is replenished either by nature or by natural processes which humanity can assist. Generally speaking, a resource is considered renewable only when it can be renewed at the same rate at which it is consumed. When this rate of renewal can be sustained, it is referred to as continuous yield.

Wind, water, solar, tidal, and geothermal energy are all forms of renewable energy. Technically, fossil fuels are also renewable, but only over impractical time periods (literally millions of years), so they do not qualify as renewable resources. Renewability does not necessarily correspond with environmental friendliness. Biomass fuels such as peat, wood and food processing byproducts, for example, may contribute substantial carbon dioxide emissions to the atmosphere, but they still qualify as renewable if they can be created as rapidly as they are consumed.

See also: