Most solar panels in the UK do not need regular cleaning. On a typical pitched roof, rain does the bulk of the work, and paying for routine cleans that your system does not need is money down the drain. Some systems genuinely do need cleaning, and for those it is worth every penny. The trick is knowing which kind you have.
We are a company that sells solar panel cleaning, so you might expect this article to say something different. Here is why it does not.
What the industry's own guidance says
Solar Energy UK, the industry trade body, publishes the standard best-practice guide for looking after rooftop solar. The current edition, from December 2025, does not recommend a fixed cleaning schedule for every system. It recommends a site-specific approach: monitor your generation, look at your panels from the ground once in a while, and clean when the conditions at your site actually call for it.
MCS, the certification body whose standard governs how systems like yours were installed, takes a similar line. Its suggested maintenance schedule for a privately owned home system involves simple owner checks in the early years, not an annual professional visit.
Panel manufacturers say much the same. LONGi, one of the largest in the world, notes in its installation manual that rainfall normally has a cleaning effect and that how often panels need washing depends on how dirty they actually get.
None of these organisations sells cleaning. That is rather the point of quoting them.
So why does anyone pay for cleaning?
Because some sites are not typical, and on those sites soiling genuinely does cost generation. The conditions that change the answer:
Bird fouling. Droppings do not wash off in rain the way dust does, and pigeons nesting under an array bring a steady supply. This is the most common reason a domestic array in the North West actually needs cleaning, and it usually needs bird proofing as well or the problem returns.
Shallow or flat roofs. Rain self-cleans a pitched roof reasonably well. The shallower the pitch, the more slowly water runs off and the more residue it leaves behind. Flat-roofed commercial arrays are the clearest case of all.
Farms and dusty environments. Agricultural dust, grain dust and dirt from ploughing settle continuously. The same goes for sites near quarries, works or busy roads.
Coastal air. Salt deposits build up and do not rinse clean.
Trees. Sap, pollen and leaf debris, plus the shading, plus the birds the tree brings.
A generation drop you cannot otherwise explain. If your monitoring shows output falling and there is no fault, soiling is one of the suspects worth ruling out.
If none of those applies to your system, our honest advice is to keep your money. Look at your panels from the ground a couple of times a year, glance at your monitoring app now and then, and get on with your life.
What about the big percentage claims?
You will see companies advertising that cleaning boosts output by 25%, 42%, or similar. Ask where the number comes from.
We looked for a credible UK study establishing a universal generation uplift from cleaning a normal domestic array, and we could not find one. Neither, as far as we can tell, can the companies making the claims. Soiling does reduce output, and cleaning a genuinely dirty array does recover generation. But the amount depends entirely on how dirty the panels were, and on a typical UK pitched roof it is usually modest. A meaningful figure would need before-and-after measurements for your actual roof, adjusted for the weather. A number in an advert is not that.
The Advertising Standards Authority has been upholding complaints about exactly this kind of claim in the solar industry, including a ruling in March 2026 against an "up to 94%" bill-saving claim. Treat any fixed percentage with suspicion, including from us if we ever slip.
If you do clean, do it properly
Two warnings that matter more than any technique:
Pressure washers can wreck panels. They can force water past seals and damage cells, and using one is a well-known way to void a manufacturer warranty. So are harsh detergents and abrasive pads. Panels are cleaned with soft brushes and pure water, nothing else.
Your roof is not worth it. Working at height kills people who thought it would take five minutes. If your panels cannot be reached safely from the ground with a water-fed pole, that is what professionals with the right access equipment are for.
The short version
Check whether any of the high-soiling conditions above describes your site. If not, do nothing, and distrust anyone who tells you otherwise. If yes, get it cleaned properly, deal with the underlying cause where there is one, and expect an honest cleaner to tell you when it is not worth doing again for a while.
That is how we run our own cleaning service. We would rather turn down a job than clean panels that did not need it, because you would find out, and you would be right to hold it against us. We clean, service and bird-proof solar systems across Cheshire, Greater Manchester and Lancashire, including systems we did not install.
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