I would love to go solar power. Unfortunately I don't have a spare $100,000 laying around to do the size that I want.I had 4 kw installed in 2010: https://www.nifty-stuff.com/solar-panels-energy-part-1.php
That was before we added a rental unit to the house, before the electric car, and before we had AC in the house... so since it's not enough, I just finished adding an additional 5 kw a few months ago... WAY overkill, but I LOVE LOVE LOVE solar.
I cleaned the panels at night between two days that had pretty much the same weather (except some clouds on 7/16 morning).
Blue bars were AFTER I cleaned the panels. Blue line was the day BEFORE I cleaned the panels.
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Not super scientific, but I'd guess the increase after washing was around 8% - 15%