Appreciate the attempts to quantify it. I haven't tried to quantify washing, but I do look at mine regularly. I doubt anything accumulates that rain doesn't handle well enough.
Messing around with ground panels is lower risk and safer than roof panels where tool extenders and ladders start to become involved. If you have roof panels, you are the biggest danger to your panels (and yourself.) Don't try to clean them, spray them, knock snow off of them. I was told this multiple times by my installer. :)
As another anecdata-point, when we did this for a now already fairly old roof installation of about 15kWp, it was more than “just about worthwhile”, since the panel area is contiguous: cost seemed to scale up less quickly than the wattage/theoretical maximum output, and the cleaning guy (solo company, IIRC) even told us it wasn’t necessary to do this every year (we hadn’t had it done even once the first decade+ of the installation’s lifetime).
So, at least in our case, definitely worth it.
Interesting; what was on the panels? What was the ROI on paying the guy?
Now I want solar panels merely so I have a reason to not have to clean my roof
Still the same leaves in the gutter, sadly, once they blow past the panels.
In many countries it is actually illegal to use tall ladder etc. owners would have to erect a scaffolding to make access for work people to clean it safely.
There are definitely some wacky nanny state rules out there… but I’m a little skeptical of “In many countries it is actually illegal to use tall ladder”
Probably the GP meant to hire people and order them to use a tall ladder. I don't think there's any country where it's illegal for you to use one outside of some kind of contract.
Tradespeople are typically independent contractors. You hire them to do a task, and they use their own judgement on which tools to use. You don't order them to use a tall ladder...
The regulations that tradespeople must obey and how they are contracted varies from one country to another.
And hopefully these independent contractors are insured. It may well be insurance requirements that limit the use of ladders.
It would not surprise me if this was a law in Germany, for example.
Stuff like this is why America continues to mog the rest of the world economically.