Solar panels should be cleaned once to 2x per year to maintain full efficiency levels. We can safely and easily clean solar panels on any kind of roof and sometimes from the ground. Please don't leave it up to the maintenance crew to clean the buildings solar panels. We use a pure water cleaning system that can allow us to reach panels 20 or more feet away without stepping on them. This is a 4-stage system that will filtrate out hardwater that causes water spots and without the need to squeegee down the panel. It just rinses spot free!