The Earth is constantly exposed to solar radiation. The Earth's outer atmosphere receives 1.367 W/m2 of which 6% is reflected, whereas 16% is absorbed. Atmospheric conditions (clouds, dust, pollution particles) reduce solar radiation by mirroring for 20% and by absorption for 3%. Having passed through the atmosphere, approximately 50% of solar radiation is visible in the electromagnetic spectrum, while the remaining part remains to be visible in the infrared spectrum.

Considering the reception, transformation and application there has been a distinction of active and passive use of solar energy. Active solar uses PV cells to convert the sunlight into electric energy. Passive solar utilizes construction materials with favourable thermal features in the buildings oriented towards solar radiation.

Eventually, the amount of solar energy reaching the Earth's surface is many times as much the sum total of non-renewable energy sources coming from coal, oil, natural gas and uranium.