I was quoted £20 for 8 panels washed with a bloody long pole, no ladders.

I didn't bother.

Not sure if that was the rate or just an off the cuff estimate but my window cleaner was charging 11 quid for my 9 windows.
I'm guessing if he could do it as a one off, early in the morning to avoid shocking the panels so a special journey then the extra few quid above a window clean seems fair.

If it was an annual event then buying my own pole kit would have been worthwhile, I found something available which worked with my Karcher.

Seems you're not lazy like me so probably getting the kit is sensible.

Gaz

 

If you do intend to wash them, try to use plain water and, if possible, soft water if you're in an area with hard water (meaning use ionised or distilled), no chemicals or cleaning agents, as that may harm the surface of the panel. I guess as a preference, do so either first thing in the morning or at dusk, so as not to interfere too much with their operation.

My panels have been up for over 3 years, and I've never washed them ever, and doubt I ever will. Rain and snow do that.

The only time I've ever considered it was when we had a dust storm full of sand from some far-off country, and it was dry for weeks afterwards.
The level of loss from my panels is unquantifiable compared to when installed, and I see no material change in similar months of the year compared to previous years; noting some level of delta will naturally occur due to solar variance across the seasons.
If that changes as the years progress, I may revisit this.

 

We have been using a local chap that comes around twice a year to clean the windows. A few years ago he offered to clean the solar panels at the same time. Neither of us can remember how much extra he charged to do this, but it cannot have been a lot, because if it was we would not have bothered with it. He is due to call again some time in the next two or three weeks so I will ask him what the panel cleaning price is.

What I can say with certainty is that the panels always work a bit better after being cleaned. We maintain a log of the generation every week and there is always a consistent improvement in generation straight after they are cleaned. I have no idea at all whether it's relevant, but the system the chap uses is a long pole with a rotating brush on the end. This doesn't use tap water, he runs it from a tank of distilled water in the back of his van.

The chap doesn't bother with a ladder, the carbon fibre pole he uses is long enough, and light enough, to be lifted single handed to the very top of the roof. It's a similar pole to the one he uses for the windows, but longer and with a different sort of rotating brush at the end.

We're not absolutely certain that the cleaning pays back the cost from more generation but our gut feeling is that it must do, based on the step change in power output we see afterwards. I do know that power and energy are not the same thing but we've had the panels for long enough now (about 12 years) to have got a sort of feel for the way they perform.

 

If they are cleaned in the middle of a hot day then it could be a boost due to them being cooled down but if the boost lasts for several days or more it seems your panels are getting quite dirty.

Gaz

 

Our panels haven't ever been cleaned... But I'm thinking the lichen might be bagging an increasing fraction of the total insolation. Do folk reckon the rotating brush-on-a-pole jobbie would shift the lichen?

 

I can get close to some of ours. Gave the bit I could reach a gentle brush with a cheap broom in the rain. Definitely removed a lot of micro-greenery.

 

Thanks @BornAgainEcoWarrior

I will give the ones I can reach a gentle brush in the rain with my cheap broom by way of an experiment.
There's some irony in making our green electricity generation work better by 'deforestation' of the lichen. But give it 150 years and they will have grown to cover perhaps half of the panel area... So needs must!

 

Yes I've been wondering this, my main concern is whether a periodic washing with some mechanical brushing is necessary to stop lichen from growing. When you look into how solar PV modules operate, lichen is really bad stuff because it causes 'hard shading' on spots of the panel, which can cause high resistance hot-spots under the hard-shaded areas and potentially damage the panels.

It also has a disproportionately large impact on power generation, hard-shading of small areas can significantly reduce the output from a panel or a string. It is not proportionate.

 

When the salesperson said the panels would be self cleaning, I was sceptical. Then after a bird left a dropping, and it disappeared within a couple of days, I was convinced. My panels are black - a decade ago, when they were installed, most were blue. The black panels heat up, drying deposits into dust, which is then removed by wind and or rain. Since 2014, there hasn’t been any noticeable degradation.

 

I paid £120 just the once to have them cleaned (16 panels) as they had moss and lichen on them. They did a great job with waterfed poles on the 15 year old panels and they looked like new again. After that I bought my own water fed poles (make sure you get the right reach) and I wash them once a year after some good overnight rain to soften up the dirt and bird muck. They now continually look new, no more moss or lichen,
I think rain generally keeps them clean, but once the moss starts, the lichen will follow, and that can be difficult to get off. Hence my preventative measures. Water poles are then just a one off cost.

 

The biggest impact of whether this is needed/warranted will depend on where you live, the level of greenery around your house/grounds, air quality, and the types of weather patterns you experience.

I live on the outskirts of a town, with no large trees near or overhanging my property, I am not on the direct flight path for planes, and am in an area that tends to have weather systems that get stuck and linger.

A visual inspection shows no obvious signs of moss or lichen, so I count myself lucky that, for now at least, this isn't something I need to concern myself with.

The methods shared may be useful in the future, although I'm confident the companies in my area offering a solar panel cleaning service would fleece me, as that seems to be the case for all trades in my part of West Sussex.

 

My original FIT installation back in 2011 used JA panels with a silver frame.
The silver bits had visible algae which looked pants but the panels themselves were never cleaned and still performed as good as new (give or take, seemingly) by the time I moved in 2023.
It's difficult to say if they were off by a few percent but were actually doing better due to the solar cycle but by far the best cleaning they ever had was when snow slipped off.

One 2-3 inch covering a year did wonders although I was always jumping up and down crying about lost generation.

Gaz

 

Unfortunately my roof profile is pretty shallow and access via the ground and poles is simply not possible; our window cleaner said he didn't have long enough poles as he'd need to stand in the middle of our very busy road and even then getting enough pressure etc wasn't possible. Another wanted to get scaffolding before he'd do it.

However, I found the pink Wet and Forget for sale, in a plastic container which attaches to a hose for the spray - it's designed for cleaning roofs, killing moss and other nasties, including lichen. It wasn't easy to position, as the spray couldn't quite reach the roof from the ground due to the angle, but I climbed up a ladder and sprayed it 'blind', holding the spray as far away from the wall as possible and in an arc which largely landed onto the panels guided by my wife (at some distance).

The result was great - the lichen stopped growing and six months later there is almost no sign of it. The wet and forget isn't cheap, at around £35, but it's a bargain solution in my position. And since cleaning the panels, I've noticed quite a few other installations with similar problems.

 

I've used wet and forget as well as spray n leave on all sorts of things.
Both work well and don't appear to cause any damage to anything.

Essentially go for the one which works out cheapest at the time.

If spraying overhead you need goggles and a mask and a mask is worthwhile if spraying the ground as the fumes can well up and choke you a bit.

They both tell you to keep pets off until dry and don't walk through it then across your lawn which I suppose some with just about enough common sense to read that bit would benefit from.

To spraying panels it would be best done on a dry but overcast day with little to no wind and no rain forecast for about 6 to 8 hours. I've never sprayed panels but imagine massive drone might be good fun to get the job done quickly.

Gaz

 

I understand there are ceramic coatings for glass. I don't have solar panels but if I did I would definitely apply a coating to make it easier to get the grime off.

 

I have zero experience - but I suspect a wipe of rainX on new/freshly cleaned panels would work…