Renewable energy is energy that is collected from renewable resources that are naturally replenished on a mortal timescale. It includes sources analogous as sun, wind, rain, runs, swells, and geothermal heat. Although utmost renewable energy sources are sustainable, some are not. Renewable energy stages in distinction to reactionary powers, which are being used far more snappily than they are being replenished. Although utmost renewable energy sources are sustainable, some are not. For illustration, some biomass sources are considered unsustainable at conventional rates of exploitation. Renewable energy constantly provides energy in four important areas electricity generation, air and water heating/ cooling, transportation, and pastoral (off-grid) energy services.