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Look up from the ground, ideally after a dry spell.
Even, light dulling across the whole array is normal and rain will handle it. Streaks, white deposits, dark patches or an obviously dirtier band along the bottom edge of the panels are not.
Most solar panels in the UK don't need cleaning. Here's how to tell if yours do.
On an ordinary pitched roof, rain does most of the work. Some sites are genuinely different, and on those a clean pays for itself. We would rather tell you which one you have than sell you a visit you did not need.
The honest answer first
If your panels sit on a normal pitched roof, away from trees, with no birds underneath and no farm or industrial dust nearby, you probably do not need them cleaned. Rain runs off a sloped panel and takes most loose dirt with it. Manufacturers generally treat panels as largely self-cleaning above roughly fifteen degrees of pitch, and LONGi, one of the largest panel makers in the world, says as much in its own installation manual.
We sell cleaning. We are telling you this anyway, because you will find it out from somewhere and we would rather it came from us.
What we will not tell you is that cleaning is pointless. Some roofs genuinely need it, some need it several times a year, and on those the difference is not marginal. The question is never "do solar panels need cleaning", it is "does this roof, in this place, with this pitch and these trees and these birds, need cleaning". That is a question with a real answer, and it is usually visible in a photograph.
The seven conditions that change the answer
Industry guidance does not set a cleaning schedule. Solar Energy UK's rooftop maintenance guide, the current edition published in December 2025, asks for a site-specific plan built from monitoring and conditions rather than a fixed interval. These are the conditions that actually move the answer.
1. Birds under or above the array
Droppings do not rinse off the way dust does, and pigeons nesting underneath produce a constant supply. This is the most common genuine reason a domestic array needs cleaning, and it usually needs bird proofing as well, or you will be paying us again next year.
2. A shallow or flat pitch
The flatter the panel, the slower water runs off and the more residue it leaves behind. Flat-roofed commercial arrays are the clearest case of all, and they are the reason the commercial side of this service exists.
3. Overhanging trees
Sap, pollen, leaf litter, and the birds the tree brings with it. Shading is a separate problem and we will look at that too while we are there.
4. Agricultural dust
Ploughing, harvest, grain drying, livestock buildings. Farms are a genuine high-soiling environment, which is why it appears as a section on our farms page rather than as an upsell.
5. Industrial or traffic grime
Quarries, works, and busy roads deposit a film that rain alone does not shift.
6. Coastal salt
Salt builds up and does not rinse clean.
7. Generation that has dropped with no other explanation
If your monitoring shows output falling and there is no fault, soiling is one of the suspects worth ruling out. It is not the first suspect. See why generation drops.
If none of those describes your site, our advice is to keep your money and look at the panels from the ground once or twice a year. That is roughly what Solar Energy UK suggests for a domestic roof anyway.
Check it yourself before you call anyone
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Look under the array from a distance.
Can you see nesting material, feathers or droppings on the roof below? That is a bird problem, not a cleaning problem, and cleaning alone will not fix it.
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Open your monitoring app.
Compare this month with the same month last year. A gradual decline that tracks a dry spell points at soiling. A sharp drop points at a fault.
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Send us the photos.
Panels from the ground, and the underside of the array if you can see it. We will tell you whether it is worth doing.
What it costs
We price commercial and farm cleaning by the day, typically £800 to £1,500 a day depending on the size of the system and how dirty it is. Smaller domestic jobs are priced individually.
Published UK cost guides put professional cleaning at roughly £4 to £15 per panel, with the spread driven almost entirely by access. What actually moves the price on a quote from us:
| Factor | Effect |
|---|---|
| How the array is reached | The single biggest factor. Ground-level water-fed pole is quick. Scaffolding or a platform is not |
| Panel count and layout | More panels, more time. A split array takes longer than one block |
| What is on there | A light film is a wash. Bird fouling, lichen or sap is a different job and we will say so before we start |
| Roof height and pitch | Two-storey and steeply pitched roofs need different access equipment |
| Whether proofing is needed too | Cheaper done in one visit than two |
We quote from photographs wherever we can, so you are not waiting on a site visit to find out what it costs.
About those percentage claims
You will see companies advertising that a clean boosts output by 25%, 42%, or some other confident number. Ask where it 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. Solar Energy UK confirms soiling reduces output, but describes the effect as site-specific, which is a different claim entirely. A meaningful figure would need before-and-after readings on your roof, adjusted for the weather either side. A number in an advert is not that.
The Advertising Standards Authority has been upholding complaints about this kind of claim across the solar industry, including a ruling in March 2026 against an "up to 94%" bill-saving headline. The pattern in those rulings is consistent: an "up to" label does not rescue a figure that most customers will never see.
So we do not publish one. What we will do is take a monitoring reading before and after, on your system, and show you what actually changed.
How we actually clean them
Purified water and a soft brush on a water-fed pole, from the ground wherever the roof allows it.
No pressure washers. They can force water past the panel seals and damage cells, and using one is a well-known route to voiding a manufacturer's warranty.
No detergents or abrasive pads. Same reason. Purified water dries without leaving the deposits tap water leaves behind, which is the whole point of using it.
No walking on your roof unless there is genuinely no other way to reach the array, and then only with the right access equipment and a method statement.
We follow your panel manufacturer's instructions, which sometimes means isolating the system first and sometimes does not. We check rather than assume.
The cleaning itself is delivered with our partner Pristine Panels, who do nothing else. We hold the electrical accreditations and sign off every job. Two specialists working as one is a better arrangement than one company claiming to be expert at everything.
Commercial, industrial and agricultural sites
This is where cleaning stops being marginal.
Flat and shallow-pitched commercial roofs shed dirt poorly. Farm buildings sit in constant dust. Industrial sites deposit a film that rain does not lift. On a large array the arithmetic also changes, because a small percentage across four hundred panels is worth considerably more than the same percentage across twelve.
What we bring to a commercial site: site-specific risk assessments and method statements before anyone arrives, the right access equipment for the roof, public and employer's liability cover of £10 million, work scheduled around your operations, and a dated report of what we found and what we did. If the array is worth inspecting at the same time, we will say so, because we are on the roof anyway and it is cheaper than a second visit. That is our maintenance service.
And a note on size. Several of the larger contractors will not quote below a couple of hundred panels. We will. The pub with forty, the care home with a hundred and twenty, the farm with one barn roof: that is ordinary work for us, not an exception.
Questions people ask
Do UK solar panels actually need cleaning?
Most of the time, no. On a normally pitched roof, rain does the bulk of the work, and manufacturers generally consider panels largely self-cleaning above roughly 15 degrees of inclination. Some systems genuinely do need cleaning, and the honest answer is that it depends on your specific site rather than on a schedule.
How do I know if mine are one of the ones that do?
Cleaning is usually worth it if any of these apply: visible bird fouling, overhanging trees dropping sap or leaves, a busy road nearby, agricultural dust, coastal salt exposure, a shallow or flat roof pitch where rain runs off too slowly to clean properly, or generation that has dropped without another explanation. If none of those apply, you probably do not need us.
Does cleaning actually increase output, and by how much?
Yes, but the honest range is narrower than the industry often claims. On a normally sited, lightly soiled array the recovery is usually low single digits. On a genuinely dirty array, with heavy bird fouling or agricultural dust, it can be considerably more. You may see claims of forty per cent or higher. Treat those with caution, because they describe extreme cases rather than typical ones.
Is it worth paying someone rather than doing nothing?
If your panels are clean and well sited, doing nothing is a perfectly reasonable choice, and we will say so. It becomes worth paying for when soiling is visible, when access makes DIY unsafe, or when your generation data shows a drop that cleaning would resolve.
Can I clean them myself?
You can, but there are three real risks. Working at height is the obvious one. Pressure washers can force water past panel seals and damage them. And detergents or abrasive pads can leave residue or scratch the glass, both of which can affect your warranty. If your panels are reachable safely from the ground with a soft brush and clean water, that is the safest DIY approach.
How much does solar panel cleaning cost?
We price by the day, typically £800 to £1,500 a day depending on the size of the system and how dirty it is, and price smaller domestic jobs individually. Published UK cost guides put professional cleaning at roughly £4 to £15 per panel depending on access. Cost is driven mainly by panel count, roof height and how the array is reached.
How often should commercial and agricultural arrays be cleaned?
More often than domestic ones, typically once or twice a year, because the conditions that make cleaning worthwhile are far more common on those sites. Flat and shallow-pitched commercial roofs shed dirt poorly, and farm environments generate constant dust and bird fouling.
Do you need to turn the system off before cleaning?
We follow the manufacturer's guidance for your specific system, which sometimes means isolating it and sometimes does not. Our teams work to method statements that cover isolation, water use and safe roof access.
Send us two photographs
One of the panels from the ground, one of the underside of the array if you can see it. We will tell you whether they need cleaning, roughly what it would cost, and whether anything else is going on up there. If the answer is that they are fine, that is the answer you will get.
We reply to every enquiry within two working days. We clean homes across the North West and commercial systems across the UK, whoever installed them.