Solar panels are usually installed at the right tilt to self-clean whenever there's a good downpour of rain. In dry areas, however, the wind can blow dust onto your panels and with a minimal panel tilt, rain might not rinse it off sufficiently. Likewise, if you live on the coast, the salt air can leave a sticky film that might impact the amount of solar power your system generates. In addition to this, bird droppings or leaves can also build up on your panels. As with most other types of electrical equipment, solar photovoltaic systems need regular maintenance to ensure they continue to function safely and efficiently.
How to clean your solar panels? First, never use an abrasive soap or cleaning sponge - the goal is to get the glass clean and clear as possible so you don't want to scratch it. Next, a pool skimmer with a soft cloth on the end should reach the really high roofs or a wash rag and some soft biodegradable soap should do the trick. The more often you clean, you might even be able to get away with just running the hose over them quickly, assuming you don't have built up bird poop or caked on dirt. Be very careful if you get on the roof, particularly because it will be slippery once you start washing panels the roof and that hose will have a tendency to pull you off the roof as you dismount.
Caution: Due to the fact that solar panels are usually installed on the rooftop, you should always hire a professional technician to clean them. The power produced by solar panels is every bit as dangerous as conventional electricity that is why it’s recommended that you call an installer or electrician for maintenance of your solar PV system.