I live in a fairly arid place (Bay Area) where it rains in winter but gets quite dry and dusty in the summer. I've had rooftop solar since 2016 and have noticed that generation decreases by as much as 8-10% when the panels are covered in summer dust.

I wonder if it's worth setting up a sort of sprinkler system so you can easily clean it by opening a valve. Maybe add a pipe with some holes in it to the top of the panel, and some flexible hose to hook it up to the next one.