just clean wfp as you would normaly, dont listen to all the rubbish you hear, i clean them all the time, solar panels are very hard wearing, and 100% waterproof, and built to last any weather conditions out there, the big commercial companys out their, want you to think they are a specialised clean, and only they can do them, they specify only clean only on certain months of the year, if you all believe that, then you are lossing out, wake up guys, its F%&*%g GLASS, and self cleaning, if that is the case why have i got so much work cleaning them?