Drew1966 is correct just think of who easily your safety glasses are scratched . The same holds true with trying to clean with high pressure spray I've seen a lot of panels damaged when someone contracted a cleaner and they used a 15° nozzle even worst is a zero° if using high pressure washer use at least a 30° preferably a 45°
wet from bottom to top wash from top to bottom. de-ionized water and a very mild wetting agent. Never spray the combiner box some panel systems can have very high voltages