How Often Should You Clean Solar Panels?
Once a year for most UK homes. Twice a year if your panels are near trees, busy roads, or heavy bird activity. Here's when to clean, what it costs, and how to tell if your panels need it.
The short answer: once a year for most UK homes. Twice a year if your panels are near busy roads, under trees, or in areas with heavy bird activity.
UK rainfall helps — but it doesn't replace a proper clean. Rain washes away loose dust, but it leaves behind the sticky stuff: pollen, bird droppings, tree sap, traffic film, and lichen. That builds up over time, and it costs you electricity.
Why Cleaning Matters
Dirty panels produce less electricity. It's that simple. Soiling reduces the amount of sunlight reaching the cells, and the effect compounds over time.
For most UK homes, soiling causes a 2–5% drop in output. In heavily soiled conditions — near farms, industrial areas, coastal properties, or under trees — losses can reach 10–25%. On a 4kWp system generating roughly 3,400 kWh per year at the current Ofgem cap rate of 26.11p/kWh, even a 5% loss is around £45 a year in reduced generation and export income.
A single annual clean is usually enough to recover most of that. Whether it's worth paying for depends on your system, your roof, and your local environment.
What Affects How Often You Should Clean?
| Factor | Impact on Cleaning Frequency |
|---|---|
| Panel angle 35°+ (steep pitch) | Less frequent — rain sheds dirt effectively |
| Panel angle under 15° (flat/shallow) | More frequent — dirt and standing water accumulate |
| Near busy roads | More frequent — traffic film and particulates |
| Coastal location | More frequent — salt spray dulls the glass |
| Overhanging trees | More frequent — sap, leaves, pollen deposits |
| Heavy bird activity | More frequent — droppings create hotspots |
| Suburban, clear sky | Less frequent — once a year is usually fine |
If your panels tick two or more of the "more frequent" factors above, cleaning twice a year is sensible. Otherwise, once a year does the job.
Best Time to Clean
Late spring (April–May) is ideal for your main annual clean. This catches the pollen season, clears winter grime, and gets your panels performing at their best just before peak summer generation.
If you're cleaning twice a year, add an early autumn clean (September–October) to clear anything that built up over summer.
Avoid cleaning in winter. Yield is low, surfaces are slippery, and freezing temperatures make water-based cleaning unreliable. UK rainfall does most of the work between November and February anyway. Also avoid cleaning in hot direct sunlight — cold water on hot glass can cause thermal shock and micro-cracks.
Professional Cleaning vs DIY
Professional Cleaning
| System Size | Typical Cost | Time |
|---|---|---|
| Small (6–8 panels, single storey) | £60–£100 | 20–30 minutes |
| Medium (8–12 panels, two storey) | £90–£150 | 30–45 minutes |
| Large (12–16 panels, two storey) | £120–£200 | 45–60 minutes |
What you get: purified or deionised water (no mineral deposits), telescopic water-fed poles (no scaffolding in most cases), soft brush agitation for stubborn soiling, and a quick visual inspection of panels and fixings.
Most professional cleaners are window cleaning firms with solar panel experience, or dedicated solar cleaning companies. Prices are typically lower in the North and higher in London and the South East.
DIY Cleaning
If you can safely reach your panels from the ground with a telescopic pole, DIY is straightforward and essentially free after the initial kit purchase (£30–£80 for a pole and brush).
The rules:
- Use deionised water only — tap water leaves mineral deposits that attract more dirt. Buy deionised water from car care suppliers, or use an inline deionisation filter on your garden hose.
- Soft brush on a telescopic pole — never use abrasive materials.
- Never use detergent or washing-up liquid — it leaves a residue that attracts more dirt and can damage the anti-reflective coating.
- Never use a pressure washer — the force can crack cells, damage seals, and void your warranty.
- Never climb onto your roof — the risk of falls is serious, and walking on panels will damage them.
- Clean on a cool, overcast day — or early morning before panels heat up. Water evaporates quickly off hot panels and leaves streaks.
DIY works well for single-storey homeswith accessible panels. For two-storey houses, steep roofs, or panels with heavy lichen buildup, hire a professional. It's not worth the safety risk.
How to Tell If Your Panels Need Cleaning
You don't need to guess — your inverter app tells you. Most monitoring apps (Fox ESS, SolarEdge, Enphase, Solis, Growatt, GivEnergy) show daily and monthly generation data.
- Compare your outputagainst expected generation for the time of year and weather. A sustained drop of 5%+ below expected output that isn't explained by weather or shading suggests soiling.
- Compare year-on-year if you have historical data — a gradual decline that recovers after cleaning confirms soiling was the cause.
If you notice a sudden sharp droprather than a gradual decline, that's more likely a fault — failed panel, inverter issue, or tripped isolator — not a cleaning problem. Check your system before booking a clean.
Find a Cleaner
We maintain a directory of solar panel cleaning companies across the UK, searchable by region.
Find solar panel cleaners near you →
Frequently Asked Questions
How often should I clean my solar panels in the UK?
Once a year is enough for most homes. Clean twice a year if your panels are near roads, under trees, or in areas with heavy bird activity. Late spring (April–May) is the best time for your main annual clean.
Do solar panels really need cleaning?
Yes. While UK rain helps with loose dust, it doesn't remove sticky soiling like bird droppings, tree sap, pollen, or lichen. Dirty panels typically lose 2–5% output, rising to 10–25% in heavily soiled conditions.
How much does professional solar panel cleaning cost?
£60–£200 per visit depending on system size, location, and roof access. Most standard residential jobs fall in the £80–£150 range.
Can I clean my solar panels myself?
Yes — if you can reach them safely from the ground. Use deionised water and a soft brush on a telescopic pole. Never use tap water, detergent, pressure washers, or climb onto your roof.
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