Involved in large scale, long term solar testing in the past: I was almost always better to let the rain clean the panels in the field, even in some pretty dus

Involved in large scale, long term solar testing in the past: I was almost always better to let the rain clean the panels in the field, even in some pretty dusty and arid climates. The deciding factor was usually the labor cost of the cleaning. (Think very depressed labor prices) Even then the risk of damage from the cleaning ops might sway away from manual cleaning.