Approximately 1.55 x 10l8 KW hours of solar energy reach the earth's outer atmosphere annually. Approximately a third of this energy is reflected back into space and some absorbed by the atmosphere while approximately half reaches the earth's surface. Actually, wind, waves, rivers and ocean thermal gradients are all the various forms of solar energy, as they exist in nature. The form that is being harnessed more and more in recent times is the photosynthetic radiation for direct use for heating or conversion into electricity using solar cells.

Solar energy accounted for 0.07 quadrillion Btu (or 0.074 x109 Giga Joules) or .075% of the total energy consumption in the U.S. in 1996.