Article URL: https://incoherency.co.uk/blog/stories/should-you-wash-your-solar-panels.html Comments URL: https://news.ycombinator.com/item?id=49069132 Points: 113 # Comments: 82

I have a small solar farm and the panels have got visibly dusty. Is cleaning them worthwhile? How much difference does it make? Let's find out. I know that my panels have not been cleaned in the last year. I expect they also weren't cleaned in the year prior to that (why would you clean them when you're about to sell the house?). But beyond that I don't know when they were last cleaned. The short answer is that I think I got a 2%-5% increase in power output from my solar farm due to cleaning the panels, which will work out to about £60-£150/yr, decaying to 0 over the course of a few years. So, probably just about worthwhile. There are 16 panels in total, connected up to the inverter as 2 banks of 8 panels each. The inverter reports the power output from each bank individually, so the plan is to take a bunch of readings before starting, then wash all of the panels in one bank, taking readings in between and at the end. We can test whether washing the panels has made any difference by looking at the ratio of power output from the 2 banks. If we just looked at raw power output then it would be confounded by changing cloud cover, sun angle, etc. There is still the fact that the 2 banks of panels are physically separate and plausibly one bank is better positioned for sun 45 minutes later than the other. Ideally I would have been measuring the ratio of power output for several days prior to see how it varies throughout the day. This is how the first row of panels looks after I've washed 3 of them, you can see the furthest one is noticeably grubbier: So they were "visibly dusty", but not massively dirty. If your panels are dirtier than mine were, then your benefit from cleaning them will be greater than mine was.