Should you wash your solar panels?

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.

Summary

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.

Methodology

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…