The basic answer is no. We should get enough periodic precipitation to clean off most of the dirt and dust accumulating on the solar panels. However, if we get one of the those periods of two months without any rain fall with a lot of pollen and dust you may want to hose off the solar panels, but it really is not all that important. But if you really want to clean the panels use a high pressure nozzle on your garden hose so you can do the washing from the ground and never up on the roof. Dawn or dusk are the best times of the day to do this so minerals in the water do not flash dry onto the panel’s glass in the heat of the sun creating a greater haze on the glass than the dirt you were attempting to clean off.
If you lose a few cents worth of production a day due to dirt, is it worth going on a roof to perform cleaning while risking a fall off a roof?? If the dirt gets heavy enough or you notice large areas of bird droppings that the rain will not wash away you may want to have the panels professionally cleaned. Some solar companies and some window washing companies will perform this task for you at a moderate fee. But usually the rain will do most of the work required to keep the panels clean.
