Personal experience:
Cleaning is not that big a deal.
I get out a hose, and spray the array. Even when the panels are pretty dirty (Arizona Dust, usually), I don't notice a big change comparing prewash to post-wash electrical output.
I do this a couple of times a year, not every two weeks, and I have never used any kind of cleaning solution. After ten years, the array is still putting out good levels of power, but I have a few panels that are not working properly that need to be repaired (probably broken leads).