<P> The total amount of energy received per second at the top of Earth's atmosphere (TOA) is measured in watts and is given by the solar constant times the cross-sectional area of the Earth . Because the surface area of a sphere is four times the cross-sectional surface area of a sphere (i.e. the area of a circle), the average TOA flux is one quarter of the solar constant and so is approximately 340 W / m2 . Since the absorption varies with location as well as with diurnal, seasonal and annual variations, the numbers quoted are long - term averages, typically averaged from multiple satellite measurements . </P> <P> Of the ~ 340 W / m2 of solar radiation received by the Earth, an average of ~ 77 W / m2 is reflected back to space by clouds and the atmosphere and ~ 23 W / m2 is reflected by the surface albedo, leaving ~ 240 W / m2 of solar energy input to the Earth's energy budget . This gives the earth a mean net albedo of 0.29 . </P> <P> The geothermal heat flux from the Earth's interior is estimated to be 47 terawatts . This comes to 0.087 watt / square metre, which represents only 0.027% of Earth's total energy budget at the surface, which is dominated by 173,000 terawatts of incoming solar radiation . </P> <P> Human production of energy is even lower, at an estimated 18 TW . </P>

Energy provided directly from earth's interior is called