This is a common question and the quick answer is “probably not”!
If you live in an area of moderate to high precipitation then there is a good chance that your array is a getting a natural cleaning once every while from Mother Nature.
And even if your modules do get a little dirty from time to time, the system designer would already have factored in the minimal loss to production when your system was sized, so the predicted energy output should not be significantly impacted.
Now sometimes a storm can pick up dust from drier areas and then rain it down on you array making it extremely dirty and significantly diminishing production. Or perhaps you happen to be unfortunate enough to be living next to a dusty construction site. In these cases, you may want to consider giving the modules a wash.
If you do decide that it is necessary, you may consider calling your solar installer to see what they might charge to come out and do a cleaning. This is probably a safer option than climbing on your roof -top yourself but of course it could be costly and the slight gain in production may not be worth the investment. Should you want to do it your self, remember that safety should come first and be sure to use fall protection at all times during the cleaning process.
Washing home solar panels is not that different from washing your windows or car windshield. All of the electrical components are sealed within the module, so it is safe to wash the glass surface, and a soapy water mix should be sufficient to remove any dust, dirt, bird droppings and the like. Using a mop or a soft non abrasive brush with an extension handle will give you the reach you need to remove any soiling from the module glass and a hose should be sufficient to spray off any residual dirt.