Do flat panels need regular cleaning though? I'm in a rainy location and was told to always have at least some tilt so that you don't have to clean them as frequently
They end up covered in moss and mud.
I'd recommend doing it at night, because I got a nasty zap off mine when presumably some of the mopping water got into the electrics and came up the metal mop pole .. (the electrics are all supposedly fully waterproof, but I guess on my 10+ year old panels stuff has degraded)