Do solar panels really need cleaning in the UK? An honest answer

Yes. We recommend cleaning solar panels one to two times a year, depending on the area they are in and what the panel warranty asks for. Rain helps on a pitched roof, but it does not shift bird droppings, farm dust, sap or salt, and it barely runs off panels that sit almost flat.

We sell solar panel cleaning, so here is what the industry's own guidance says, alongside our own advice.

What the industry's own guidance says

Solar Energy UK, the industry trade body, publishes the best-practice guide for looking after rooftop solar. The current edition, from December 2025, covers cleaning for homes and businesses and treats every installation as different, rather than setting one schedule for every roof.

MCS, the certification scheme whose standard governs how systems like yours were installed, takes a similar line. Its advisory maintenance schedule asks someone who owns their home for a yearly look at the panels from the ground. It lists cleaning "particularly where shallow pitch and dusty environment", not as a yearly job for everyone.

Panel makers say much the same. LONGi, one of the largest in the world, says in its installation manual that rainwater normally cleans the panel surface, and that how often panels need cleaning depends on how fast dirt builds up.

The Energy Saving Trust suggests checking your panels every 12 to 18 months and cleaning them if there's visible dirt.

Our own recommendation is one to two cleans a year, depending on the area and on what the panel warranty dictates. The guidance above is why the area matters so much: the same panels need less on a steep roof in clean air than on a shallow one next to a farm.

Should I clean my solar panels? What decides how often

Yes, and these are the conditions that push a roof towards two cleans a year rather than one:

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 home array gets dirty fast, and it usually needs bird proofing as well or the problem returns.

Shallow or flat roofs. Rain 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 sites. Agricultural dust, grain dust and dirt from ploughing settle all the time. The same goes for sites near quarries, works or busy roads.

Coastal air. Salt builds up and does not rinse clean.

Trees. Sap, pollen and leaf debris, plus the shading, plus the birds the tree brings.

A drop in generation 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, one clean a year is usually enough. In between, look at your panels from the ground now and then and glance at your monitoring app.

How often do solar panels need to be cleaned?

On a house: one to two times a year, depending on the area and what your panel warranty asks for. A steeper roof in clean air sits at the lower end; any of the conditions above push it towards two. A yearly look from the ground, as MCS suggests, tells you when one is due.

On commercial and farm sites: once or twice a year, depending on the site and what the panel warranty asks for, to keep up with the warranty and the efficiency of the array. Flat roofs, yard dust and birds around farm buildings mean these sites usually sit at the top of that range.

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. Soiling does reduce output, and cleaning a genuinely dirty array does recover generation. But the amount depends entirely on how dirty the panels were. 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 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

Our guide on how to clean solar panels yourself goes through what the panel makers allow. Two warnings 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's warranty. So are harsh detergents and abrasive pads: LONGi's manual rules out acid and alkaline cleaners and anything rough on the glass. 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.

Do solar panels need servicing as well?

Cleaning and servicing are different jobs. Cleaning deals with what is on the glass; a service checks the wiring, the connectors, the fixings and the inverter, the parts that fail quietly. We recommend an inspection every one to two years, as the Energy Saving Trust does. MCS's advisory schedule for a home you own is the minimum: your own yearly look and a visit by an MCS installer at about 10 years. Our servicing page explains what a service covers and what it costs.

Key points

We recommend one to two cleans a year. How many depends on the area and your panel warranty; rain helps on a pitched roof but doesn't shift everything.

Birds, farm dust, sap, salt and flat roofs mean the top of that range. Bird mess usually needs proofing too.

Commercial and farm sites: once or twice a year, to keep up with the warranty and the efficiency of the array.

Never use a pressure washer or detergent, and don't go on the roof yourself.

Our cleaning service uses purified water and soft brushes, and we tell you from a photo whether your panels are due before anything is booked. We clean, service and bird-proof solar systems for homes, businesses and farms across the UK from our base in Warrington, including systems we did not install.