The fundamental requirement for solar energy systems is the presence of direct sunlight. Solar panels convert sunlight into usable electricity through the photovoltaic effect. Depending on the density of the clouds, a stormy day can cause anywhere from a small to a very. The good news is, panels are designed to capture energy from a variety of light conditions, making them effective even on cloudy or snowy days. Types. Peak sun hours, typically between 10 a. This process necessitates the absorption of photons, which energizes electrons in the solar cells, leading to the.