Do solar panels need cleaning?
On most UK roofs, rain does most of the work. Clean when dirt stays put and your output shows it, and leave anything at height to someone with the right access.
Usually not on a fixed schedule, unless your panel manual sets one. On a pitched UK roof, regular rain washes off most dust and pollen, so cleaning is worth it when dirt sticks and stays: bird droppings, lichen or moss along the bottom edge, or grime on a flat or shallow-angled array. Clean when that dirt is still there after rain and matches a drop in output you've actually checked. If the panels are on a roof, use a professional with proper access equipment: a few extra kWh are never worth a fall.
This guide covers the decision to clean and how it should be done. For the inverter, wiring, roof fixings, monitoring and paperwork, see our solar panel maintenance guide. Cleaning and maintenance aren't the same service, so check what a contract actually includes.
What makes panels dirty, and what rain washes off
Different deposits behave differently:
My yearly electricity use is
Your yearly electricity use helps us size your solar panel system.
- Dust, traffic grime and pollen usually form a thin, even film that rain removes on a sloping roof.
- Bird droppings are the worst deposit: opaque, concentrated and stuck fast. Roofs with pigeons nesting nearby, or under the panels, get them repeatedly.
- Lichen, moss and algae grow where water sits, typically along the bottom edge of each panel and the frame, and are common in damp, shaded spots.
- Leaves and debris collect near trees and gutters.
- Sea salt can build up near the coast.
The angle matters. Trina Solar, for example, recommends mounting its panels at 10° or more partly so that rain washes dust off, and says panels laid flat need cleaning more often because they don't self-clean. Most pitched UK roofs are much steeper than that. Flat-roof arrays on low-angle frames, and panels under trees or near bird roosts, are the ones most likely to need attention.
A small opaque patch matters more than its size suggests. Panels are wired in groups, and a dropping over part of one cell can hold back more than just that cell. Our guide to solar panel shading explains why.
| What you see | First step | Why |
|---|---|---|
| Light, even dust with regular rain | Watch before paying for a clean | Rain usually deals with it |
| Bird droppings that stay after rain | Book a targeted clean or inspection | A local opaque patch can cost more output than it looks |
| Moss or lichen along the lower edge | Ask for a clean and a check of the frame and roof | Trapped damp and debris can build up |
| Leaves around the panels or in gutters | Have them cleared safely | Blockages and water flow can matter as much as the glass |
| Sudden drop in output across the whole system | Check the inverter and app alerts first | Dirt doesn't explain a sudden stop |
| Cracked glass, exposed cable or a burning smell | Keep people away and call your installer | That's a safety problem, not a cleaning job |
Check the effect before you pay
Don't judge from the ground by the colour of the glass. A dip in output can come from cloud, a new shadow, heat, an inverter fault or a monitoring glitch. Compare periods in the same season with similar weather, and use the generation figure from your inverter or monitoring app, not your bill or your export: what you use at home changes independently of what the panels produce. If two similar roof faces are monitored separately, a persistent gap between them is a clue, though not proof on its own.
Don't multiply one good day by 365. A clean done just before a sunny week can look miraculous simply because the sun came back. If a company quotes a percentage gain, ask what production and weather data it's based on, and ask for before-and-after photos.
Worked example (illustrative). Take a 4 kWp south-facing system in London. PVGIS estimates about 1,019 kWh per kWp a year, so about 4,075 kWh (4 × 1,018.84). Suppose stubborn dirt cost 2% of that over a year: 4,075 × 0.02 = 82 kWh. If you'd have used all of it at home instead of buying it at the Ofgem price cap unit rate for October to December 2026 (26.32p/kWh, no VAT), it's worth about £21. If you'd have exported it on E.ON Next's Flex Export tariff (6p/kWh, variable, open to customers of any supplier, as of 23 September 2026), it's worth about £5. The 2% is an assumption to show the scale, not a UK average: a heavy local deposit could cost more, and light dust that rain removes could cost almost nothing. Compare that figure with the cleaning quote.
How panels should be cleaned
The equipment matters more than the technique, because the wrong equipment causes the damage. Whoever does the cleaning, and only from the ground or with proper access:
- Water and a soft brush are usually enough. Use a soft, non-abrasive, non-conductive brush or sponge. No scouring pads, scrapers or wire brushes: the glass is toughened, but its anti-reflective coating can scratch.
- Use purified or soft water if you can. In hard-water areas, tap water drying on the glass can leave limescale marks. Professional window cleaners' water-fed poles use purified water for this reason.
- Skip the detergent unless the manufacturer allows it. Some manuals permit a mild cleaner for greasy dirt; strong acids, alkalis and solvents are ruled out.
- Don't improvise with a pressure washer or steam cleaner. Manuals differ: Trina's Vertex manual, for example, bans steam cleaners and sets a maximum water pressure, while other makers set different limits. Forcing water into the frame edge, junction box or connectors can damage the panel. If you don't know your panel's limit, don't use pressure.
- Avoid hot glass. Cold water on panels that have been in full sun is a thermal shock. Clean early in the morning, in the evening or on a dull day.
- Never stand, kneel or lean on panels. It can cause micro-cracks in the cells that you can't see and that show up later as lost output.
Your panel manufacturer's manual is the rule, not a general recipe. It sets what's allowed and warns that improper cleaning can void the warranty. Get the manual for the exact model on your roof: your installer's handover pack should include it.
Some panel manuals do set a routine: JinkoSolar's, for example, recommends cleaning preferably once a month, and more often in dusty conditions. MCS's advisory maintenance schedule for UK installers lists cleaning mainly for shallow-pitched arrays in dusty places. Check your own manual, because its conditions are what count for your warranty.
Why you shouldn't go on the roof yourself
This is the part most guides skip, and it decides the question. Cleaning panels on a roof means working at height, on a slope, on a surface you're making wet, with a long pole shifting your balance. The risk is a fall.
There's an electrical risk too. Panels in daylight produce enough voltage to give a dangerous shock, and cracked panels are more hazardous when wet. Never open connectors, isolators or the inverter to clean, and don't assume switching the inverter off makes the panels safe.
If you can reach the panels safely from the ground, for example a ground-mounted array or a low outbuilding, with a water-fed pole that stays well clear of overhead power lines, cleaning them yourself can be reasonable. Otherwise, pay someone equipped for it. In Great Britain, a business working on your roof is covered by the Work at Height Regulations 2005 and has to plan the job and use suitable access; the Health and Safety Executive says ladders suit only low-risk, short-duration tasks. Many cleaners work from the ground with water-fed poles; if the panels need hands-on work, expect scaffolding or other proper access.
If pigeons are nesting under your panels, cleaning alone won't last. Ask about bird mesh around the edge of the array, ideally fitted while scaffolding or other access is already in place, because fitting it later usually means paying for access again. In England, Wales and Scotland it's an offence to damage or destroy a wild bird's nest while it's in use or being built, so check for active nests before any work is done.
What a cleaning quote should say
A quote should state:
- the number of panels and how they'll be reached (ground-based pole, cherry picker, scaffolding);
- the method, the water (purified or not) and any cleaning product, and that it follows the panel manufacturer's instructions;
- whether it includes anything beyond washing the glass: clearing leaves, a visual check of the panels and fixings, before-and-after photos;
- who pays if something is damaged during the work, and whether the company has public liability insurance;
- whether it's a one-off or a recurring plan, and how to cancel.
By law, a trader has to carry out a service with reasonable care and skill (Consumer Rights Act 2015). That gives you a route if a careless clean damages your panels, but it's much easier to use when the scope was written down first.
Compare the price with the problem. A one-off clean makes sense after a specific event, such as pigeons moving in, or on a site that gets dirty quickly. A yearly plan only makes sense if your own observations show dirt coming back regularly. The word "maintenance" on an invoice doesn't mean anyone checked the inverter, cables or roof: if you want that too, see what a maintenance visit should cover.
Cleaning and your warranty
Your panel warranty covers defects and output over time, not damage from careless cleaning. Manufacturers say so directly: Trina, for example, states that damage from failing to clean or cleaning improperly voids its warranty. Read the maintenance and cleaning conditions in your panel's warranty document and manual before anyone puts a brush on the roof. Our guide on how long solar panels last explains what the different warranties cover.
Decide by setup
- Pitched roof, open surroundings, regular rain: start with a look from the ground and your monitoring data. If nothing persists, there's no reason to book a "preventive" clean just because a year has passed.
- Flat or low-angle array, or near trees or roosting birds: note the deposits that keep coming back. You may need cleaning more often, but your own observations set the interval, not a national rule of thumb.
- Ground-mounted panels: access is easier, but the electrical risk and the manual's rules still apply.
- Cracked panel, scorch marks or water behind the glass: stop. Report it to your installer. Scrubbing a damaged panel can make things worse.
Before booking, answer four questions: what's dirty, since when, which output is affected, and how can the panels be reached safely? If you can't answer yet, start with photos and monitoring readings.
Frequently asked questions
How often should solar panels be cleaned in the UK?
There's no interval that fits every home. On a pitched roof with regular rain, many systems go long periods without needing a clean. Clean when a deposit is visible, stays after rain and shows up in your output data. Flat arrays and panels near trees or birds usually need it more often. Check your panel manual too: some recommend a routine.
Does rain clean solar panels?
Mostly, on a sloping roof. Rain removes dust and pollen from tilted panels; manufacturers such as Trina recommend a tilt of at least 10° for this reason. It won't reliably shift bird droppings, lichen or moss.
Can I use a pressure washer on solar panels?
Don't improvise with one. Manufacturers set their own limits, some ban steam cleaners, and forcing water into the frame edges or connectors can damage the panel and affect your warranty. Soft water and a soft brush are the safe default.
Can I clean my solar panels myself?
Only if you can reach them safely from the ground, for example with a water-fed pole, without standing on the roof or on the panels, and following the manufacturer's manual. Otherwise, use a professional with proper access equipment.
What should I use to clean solar panels?
Soft or purified water and a soft, non-abrasive brush or sponge. Avoid abrasive pads, scrapers, strong chemicals and solvents unless your panel's manual specifically allows a product.
Is cleaning covered by my solar warranty?
No. Warranties cover product defects and output, not cleaning. Some manufacturers say damage from improper cleaning voids the warranty, so check the manual for your exact model first.