Do Solar Panels Need Cleaning After Rain?
Rain doesn't actually clean your solar panels the way you think. Here's the truth about rain and soiling.
Rain rinses light dust but bakes on bird droppings, salt, and pollen — the hard-to-remove stuff that actually costs you production. The 'rain cleans my panels' assumption is one of the most expensive misconceptions in residential solar.
Why rain bakes on droppings
Bird droppings are alkaline and rich in uric acid. Rain wets them, then sun bakes them back on harder than before — sometimes etching the anti-reflective coating beneath. A dropping that would wipe off in week one becomes a permanent shadow by month three.
What rain actually rinses off
Rain does a decent job on loose surface dust if it's heavy enough to flow rather than just dampen. In a typical San Diego year that's maybe 10–15 events. The rest of the time, rain just enough to spot the glass with mineral deposits and leave the real soiling in place.
The post-rain cleaning misconception
If anything, the right move is to clean shortly BEFORE the wet season starts, not after it ends. That way you enter winter clean, the rain handles the easy stuff, and you come out the other side ready for spring. Saturn's fall slot does exactly that.