I am Jason Pope from Selec Group, a solar installation company based in Cambridgeshire. One of the questions people ask me most is whether they need to clean their solar panels. Like a lot of my answers, it depends. For most homes the honest answer is no, the weather does the work for you. But there are a few situations where a clean pays off, and it is worth knowing which camp your roof falls into. Here is the straightforward version.
For most roofs, let the rain do it
If you have a standard pitched roof that is not too shallow, you can mostly forget about cleaning. Here in the UK we get plenty of rain, and that rain washes the panels for you with no effort on your part.
The panels I was looking at when I filmed this are a good example. South facing, a fairly standard roof pitch, nothing unusual. Mother Nature will keep those clean. Unless something out of the ordinary lands on them, I would be very surprised if they ever needed a proper wash in their working life.
The pitch matters here. A reasonable angle means water runs off and takes the dust and grime with it. The steeper and cleaner the run off, the less anything has a chance to settle and stick. For the typical Cambridgeshire roof, that is exactly what happens, season after season.
When a clean is worth it
There are a handful of situations where the rain alone does not keep on top of things. These are the ones to watch.
- North facing arrays. A north facing roof gets less direct sun and stays damper for longer. Over a number of years you can get a build up of moss, and it often starts in the spot where water sits rather than running straight off. Left long enough, that may eventually warrant a wash.
- Bird mess. This is the big one. A heavy covering of droppings sits on the glass, does not rinse off easily, and shades the cells underneath. If your panels are getting hit with bird mess, a clean makes a real difference.
- Tree sap. If you have trees overhanging the roof, sap is sticky and rain does not shift it. Same story, it sits there and blocks light.
- Shallow and flat roofs. A shallow pitch means water does not run off cleanly, so dirt has more chance to settle and stay. Over time those panels can need attention that a steeper roof never would.
If your panels fall into one of these groups, an occasional clean is sensible. For everyone else, it really is not something to worry about.
A word on flat roofs
There is a nice quirk with flat roofs that is worth mentioning. They are the most likely to need cleaning, because the shallow angle lets dirt settle, but they are also the easiest to clean.
On a flat roof you can usually get up there safely and give the panels a wash yourself, or have someone do it without scaffolding or risky ladder work. So while a flat roof array might ask for a clean more often, the job itself is far simpler than reaching panels on a steep pitched roof. The two things roughly cancel out.
How to keep cleaning to a minimum
A few sensible choices at install stage cut the cleaning you will ever need. This is part of doing a job properly rather than just bolting panels on.
The biggest one is bird proofing. We fit a black wire mesh skirt around the edge of every array as standard. Its main job is to stop pigeons nesting in the gap under the panels, but it also keeps the area cleaner and tidier, because you do not have birds living and messing right on top of your investment. It is cheap and simple to fit while the scaffold is up, and a real nuisance to add later.
Beyond that, sensible siting helps. Where we can, we avoid putting panels directly under heavily overhanging branches that will drop sap and leaves. And the steeper, cleaner pitches that shed water well need the least attention of all.
What about cleaning kits and contracts?
You will see companies selling regular solar cleaning contracts. For most domestic roofs in this country, you simply do not need one. The rain is free and it does the job. Do not let anyone talk you into paying for something the weather already handles.
If you genuinely do have a problem, bird mess on a steep roof for instance, then get someone with the right access equipment to do it safely. Cleaning panels is not worth a fall off a ladder. We do not work off ladders for installs and you should not climb up to clean panels off one either.
The bottom line
For most homes the answer is no, you do not need to clean your solar panels. UK rain washes a standard pitched array all by itself. The exceptions are north facing roofs that grow moss, panels hit by bird mess or tree sap, and shallow or flat roofs where dirt settles. Bird proofing at install time keeps things cleaner from day one. We fit it as standard across Cambridgeshire, Bedfordshire and Northamptonshire. If you are weighing up solar and want it done properly the first time, call the office on 01480 400607 or request a survey through our website.
Jason Pope
Owner, Selec Group