For the most part, natural precipitation will clean your modules sufficiently to maintain electricity production. Your modules may benefit from being cleaned from time to time if they are installed at a shallow tilt angle or you live in a dusty and dry climate. Never use chemicals or soap of any kind. If your modules are easy to access and/or spray water on, you can do this with little risk. We strongly recommend calling in a professional if you have to climb on your roof to clean them. The hospital bill if you fall off the roof will never be offset by the additional electricity production!