In most climates and situations you do not need to clean your solar panels.
Typically the pitch of the roof/racking will prevent significant dust and dirt buildup affecting your solar systems energy production and rain will take care of the rest. Even the in-frequent rain the the desert is enough to keep panels in the deserts of the South Western United States clean and producing at peak performance!
Recent studies have shown that you lose less than 1% production from dusty/dirty panels. The loss in production is minor compared to the average cost to clean panels.