i gave mine a clean there was a fair few spots on it and a shitload of dust.
they have been up for 6 months
i cleaned them the day after and halfway into the day for my comparison days to see the difference immediately and also the next day would be the best comparison
temps were very similar and no clouds either day except for a tiny bit towards the end.
dark green is day 1 light green is day 2
the first arrow is when i started cleaning them, i shadowed them while cleaning so that’s the quite sharp drop off.
my only assumption is they increased slightly due to being a cooler temp with the water for cleaning once they warmed back up it didn’t show any difference
i just used rain water and a windows squeegee thing
i cant see any justification to pay someone to clean the panels where the cleaning will pay for the clean before needing to be redone