The electricity yield of a photovoltaic plant is highest on a clear day in early summer with moderate temperatures. However, light energy is converted into electricity even if skies are overcast or in the period shortly after dusk (diffused glare-free light). The ratio of direct to diffuse radiation in Germany is approx. 60:40. The resulting energy content is used to determine the so-called annual solar radiation value. In Germany this (regionally varying) value lies between 900 and 1,200 kWh/m2 and serves as a reliable measure for the calculation of the energy production of solar plants.

In combination with other forms of regenerative energy, photovoltaics are particularly effective in capturing the peak load in the energy supply. In view of the continuous development of efficient storage technologies, however, it will also become increasingly possible in the next few years to capture the basic load of the energy supply through regenerative forms of energy. Thus traditional fossil and atomic-powered plants will no longer be needed.