Do solar panels actually need cleaning — doesn’t the rain do it?
The short answer: No — rain doesn’t clean panels, it just redistributes the grime into a thin cloudy film and leaves the worst contaminants behind. Bird droppings, lichen, moss, pollen and traffic film all sit on the glass and block light. Dirty UK panels typically lose around 2–7% of their output, rising to 10–15% in dusty or urban spots and up to ~25% in severe cases[5]. Worse, on a string-inverter system a single bird dropping can drag a panel’s output down 20–30%, because the whole string is limited by its weakest cell. A clean array generates more — which is why an £80–£150 clean[1] often pays for itself in recovered generation over the year.
The Surrey solar-soiling matrix
Original analytical contribution: the matrix below maps the situations a Surrey solar array can be in to its typical output loss, the contaminant driving it, and how often it should be cleaned. No competitor publishes a per-situation soiling matrix — they default to a single per-panel price.
| Array situation | Typical output loss | Main contaminant | Recommended cleans/yr |
|---|---|---|---|
| Under trees (Mole Valley / North Downs canopy) | 10–25%[5] | Bird droppings, lichen, sap, leaf litter | 2–3 |
| Near a busy road | 7–15% | Traffic film, road dust | 2 |
| Gatwick flightpath (Horley / Crawley) | 5–12% | Airport-area dust, particulates | 2 |
| Low-tilt bungalow array | 7–15% | Standing dirt & moss (rain doesn’t run off) | 2–3 |
| Standard 2-storey, open aspect | 2–7%[4] | Pollen, general dust, occasional droppings | 1–2 |
Loss figures reflect published UK soiling ranges[5][4]; a single bird dropping can cut a panel 20–30% on a string system. Low-tilt bungalow arrays soil faster (rain doesn’t self-rinse) but are cheaper to clean from the ground at around £2 per panel[2].
Why pure / deionised water — never detergents or pressure
The front glass on a PV panel carries a delicate anti-reflective coating. Abrasive pads, scouring and harsh chemicals can scratch it and reduce output, so we use only soft non-abrasive brushes and water. We run mains water through reverse-osmosis / deionising filtration to strip out the dissolved minerals — that’s what lets it dry spot-free and streak-free with no detergent, so there’s no residue left behind to attract more dirt. We never pressure-wash the panels: high pressure can force water past the seals and frames and damage cells. Many PV manufacturers specify periodic cleaning as a maintenance condition, so a documented pure-water clean helps keep your warranty cover intact.
Why we never walk on your roof
We clean from the ground using a telescopic water-fed pole that reaches typical 2-storey roofs. That keeps our technicians off the roof and away from the live DC wiring. Solar arrays are energised by daylight and can’t simply be switched off at the panel, so non-contact cleaning from ground level is genuinely safer — for you, your property and the panels. It’s also why we work in line with the Work at Height Regulations 2005, and clean early morning or on overcast days when the glass is cool to avoid thermal shock to hot panels. Where an array genuinely can’t be reached from the ground, we’ll tell you and arrange the right trained-operative height access rather than risk it.
Will cleaning improve my output — is it worth it?
Yes. Removing soiling restores lost generation. On a clean open array that’s usually a few percent; where there are bird droppings or biological growth it can be far more, because of the string “hot-spot” effect — one dirty or shaded cell drags the whole string down to its weakest point. Soiling also raises panel temperature, and output falls roughly 0.2–0.5% per °C of temperature rise, compounding the loss beyond the light blocked. Put simply: an £80–£150 clean[1] that recovers several percent of your annual generation typically pays for itself within the year. Check your inverter or monitoring app — if generation has quietly dropped, soiling is usually the culprit.
How often should Surrey panels be cleaned?
Once or twice a year for most homes — ideally spring and autumn. Clean more often if you’re under trees, near a busy road or the Gatwick flightpath, on the coast, or your roof is low-pitched so dirt and moss sit on the glass instead of running off. Across Surrey the tree canopy of the Mole Valley and North Downs plus heavy spring pollen tends to push frequency up. The easiest way to stay on top of it is to book a recurring spring + autumn clean so generation stays high year-round — just ask when you call.
What’s included — and the bundle option
A proper solar clean isn’t just a wipe-over. It’s the full pure-water method, done from the ground, with the panels left clear and spot-free. Here’s what every job includes:
- Ground-level access assessment before we start
- On-site RO/DI filtration to pure water (zero dissolved minerals)
- Soft, non-abrasive brush head designed for PV glass coatings
- Targeted removal of bird droppings, lichen, moss, pollen and traffic film
- No detergents, no chemicals, no pressure washing on the panels
- Spot-free, streak-free pure-water rinse and dry
Because the same access setup reaches your gutters and windows, a solar clean is easy to bundle with gutter clearing or window cleaning on the same visit — one trip, one setup, less hassle. Mention it when you call and we’ll quote the lot together.
Areas we cover
Across all of Surrey within 20 miles of Redhill (RH1) — covering RH1–RH11, CR3, SM7 and KT17–KT24. That includes Redhill, Reigate, Crawley, Horley (Gatwick), Dorking, Banstead, Caterham, Godstone and the rest of all 15+ areas.
Useful guides
Want to dig deeper before you book? Solar panel cleaning cost guide · How often should solar panels be cleaned? · DIY vs professional solar cleaning
Sources
Pricing and efficiency figures on this page are sourced from public UK cost guides and published soiling data.
- Checkatrade — Solar Panel Cleaning Cost Guide 2026. Typical £4–£15 per panel; average domestic job ~£150. checkatrade.com — solar panel cleaning cost. Accessed 16 Jun 2026.
- MyJobQuote — Solar Panel Cleaning Cost 2026. Per-panel pricing, ground-level (~£2/panel) vs roof-access (~£4+/panel), minimum charge on small arrays. myjobquote.co.uk — solar panel cleaning cost. Accessed 16 Jun 2026.
- Airtasker UK — Solar Panel Cleaning Cost. Per-visit totals by array size. airtasker.com — solar panel cleaning cost. Accessed 16 Jun 2026.
- Energy Saving Trust — Solar panel cleaning & maintenance. Typical soiling loss and recommended cleaning frequency. energysavingtrust.org.uk — solar panel cleaning & maintenance. Accessed 16 Jun 2026.
- Sentrex — The 12 costly problems caused by dirty solar panels. Output-loss ranges (2–7% typical, 10–15% urban/dusty, up to ~25% severe) and the string hot-spot effect. sentrex.co.uk — dirty solar panel problems. Accessed 16 Jun 2026.
