My solar installer advised me not to clean my solar panels - just let the rain do it. And mostly I've done that. They were installed June/July of 2014 and the first couple of years I got up there with a mop and a hose and cleaned them, but its a 2-hour pain in the a@@ and I've been lazy.
Well, today I finally got up there and cleaned them again, and based on my Enphase system and my Neurio, I'm now getting 10-12% more power.
The sun has been mostly shining yesterday and today. There are some clouds, but when they clear the panels go to max power. Yesterday that was 4.9kw. Today, so far (its right at noon as I type) I am getting max peaks of 5.4kw.
Moral of this story, clean your solar panels!
See picture - I took this just now to show you my panels and guess what! I missed one DAMMIT. (clearly visible in the picture) Now I have to crawl back up there... But it gives you an excellent "before" and "after" what the panels look like.
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Below shows the first panel I cleaned. I sat the mop on the panel next to it, which killed that panels production. So you can compare the output of the topmost panel after cleaning, with the bottom panels. Clear improvement.
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