Solar Panel Cleaning

Dirty panels lose output. How much they lose, and whether cleaning is worth paying for, depends entirely on your roof — and plenty of companies will happily take your money either way.

We will tell you straight whether yours need doing.

Do solar panels actually need cleaning?

In the UK, rain does most of the work. A panel at a decent pitch on an exposed roof sheds dirt reasonably well, and for a lot of domestic installations the honest answer is that cleaning every year is a waste of money.

Cleaning is worth it when one of these applies:

• Low pitch. Below about 15 degrees, water sits rather than runs, and dirt builds up along the bottom edge of every panel. In-roof arrays on shallow modern roofs are the usual culprits.
• Trees overhead. Leaf litter, sap and bird mess do not wash off. Birds are the single biggest cause of real output loss we see.
• Agricultural, industrial or dusty surroundings. Farm dust, pollen and construction dust bond to the glass.
• Coastal or heavily trafficked locations. Salt and traffic film build a film that rain alone does not shift.
• Flat or near-flat commercial roofs. These need it most and get it least.
• Moss and lichen creeping in from the roof tiles. Once it reaches the frame it holds moisture against the panel edge permanently.

If none of those apply to your house, we will say so rather than book you in.

What the losses look like

A light, even film of dust across an array typically costs a few percent. That is real but small — on a 4 kWp domestic system it might be £10 to £20 a year, and it is not worth a cleaning bill.

Localised soiling is different and much worse. Bird mess, a leaf dam along the bottom edge, or lichen across one row shades cells completely. Because panels are wired in series within a string, one badly soiled panel drags the whole string down. That is where you see 10%, 20% or more disappear, and that is where cleaning pays for itself quickly.

This is also why we would rather look at your monitoring data or a few photos before quoting. If one string is underperforming and the other is fine, the cause is usually localised soiling or shading, and cleaning will fix it. If both strings are down evenly, cleaning is probably not your problem — and we would rather find the real fault.

How we clean them

Pure water, fed pole, no detergents, no abrasives, no pressure washers.

Deionised water dries without leaving mineral spotting, which is the whole point — a panel cleaned with tap water looks worse a week later than it did before. The brush head is soft and the pole reaches most domestic and school roofs from the ground, which means no scaffolding cost and no one walking on your roof.

What we will not do: pressure wash panels, use anything caustic, or walk across an array to reach the far side. Microfractures in the cells are invisible on the day and show up as dead strings a year later. We have been called out to repair the results of both.

For commercial and flat roofs where pole access is not practical, we quote the right access method as part of the job — MEWP, roof access with harnesses and a proper RAMS, whatever the site needs.

Schools and commercial sites

We clean school arrays across the area, including multi-site academy trusts, and we work to the school calendar rather than ours — half terms and holidays, with RAMS and safeguarding arrangements agreed in advance and DBS-checked operatives on site.

School and commercial arrays are where cleaning genuinely pays. They are usually larger, often on low-pitch or flat roofs, frequently surrounded by trees or playing fields, and almost always unmonitored by anyone with time to notice a drop in output. We have seen school arrays running at a fraction of their capability for years because nobody was looking.

If you are a business manager or estates lead, we can take a look at your generation data before quoting and tell you whether cleaning is the right spend or whether something else is wrong.

What it costs

Domestic cleans are £10 per panel plus VAT, with a minimum charge for a single visit — so a typical 10 to 14 panel domestic array is £100 to £140 plus VAT.

Commercial and school sites are quoted per site after a look at the roof, the access and the array size. Larger arrays come down substantially per panel. Annual or six-monthly contracts across multiple sites are cheaper again, and that is how most of our school work is arranged.

Access is the variable that moves the price, not the cleaning itself. A conservatory roof, a three-storey elevation or a flat roof with no edge protection all change the job.

While we are up there

Because we install and maintain these systems rather than only clean them, we look at the array properly while we are on site and tell you what we see: lifted or loose clamps, degraded cable ties, cables resting on tiles, bird nesting under the array, corrosion on the frame, delamination or browning on the cells, and whether your bird-proofing has failed.

That costs you nothing extra and it is the part most cleaning companies cannot offer, because they are window cleaners with a pole rather than MCS installers.

If we find something that needs fixing, we will tell you whether it is urgent, whether it affects your warranty, and what it would cost — and you are under no obligation to use us for the repair.

Bird proofing

If birds are your problem, cleaning alone is a treadmill. Pigeons nesting under an array will foul it again within months and the nesting material itself is a fire and a pest risk.

Mesh clipped to the panel frames — never screwed or drilled — closes the gap around the perimeter without touching the roof covering or voiding the panel warranty. It is usually best done at the same visit as a clean, since the array has to be clear first.

Book a clean, or ask first

We cover Milton Keynes, Buckinghamshire, Bedfordshire, Oxfordshire and Northamptonshire.

Send us a photo of your array and your recent generation figures and we will tell you honestly whether it needs doing. If it does not, we will say so — and if something else is wrong with the system, we can usually spot it from the data before anyone visits.

We also handle solar panel installation, battery storage and system repairs, so if the clean turns into a fault find you are already talking to the right people.