Why should make solar panels clean?

Solar panels are designed to absorb sunray as a source of energy for generating electricity or heating.

Due to an angle of solar panels, they are more prone to drop birds. Just rain does not wash away the dust, dirt, remaining of bird dropping on a solar panel. The build-up of dust, dirt, pollen, bird dropping and other debris reduces the amount of light hitting the panels and adversely affect optimal Solar Panel Efficiency.