Solar panels need to be cleaned in order to operate at their maximum efficiency. Most solar panel systems use a glass coating to protect solar cells. Dust and dirt settle on the protective glass panels; as the material accumulates, it gradually decreases the amount of sunlight the solar cells receive. Keeping the glass panel faces clean maximizes the system's ability to generate electricity. In some cases, a solar panel could lose as much as 30% of its efficiency if the panel were never cleaned.