Do solar panels need cleaning in the UK? What really affects output

Updated 6 November 2026 · By the Solar Panel Cleaners team

Short answer: Many UK solar panels stay reasonably clean thanks to rain, so light dust usually costs only a small amount of output. Cleaning makes a real difference when panels have bird droppings, lichen, moss or a heavy film of grime, are low-pitched, or sit near trees, farmland, the coast or busy roads. The Energy Saving Trust suggests checking them every 12 to 18 months and cleaning if they are visibly dirty.

Why dirt matters

Solar cells generate power from the light that reaches them. An even film of dust only trims output slightly, but concentrated dirt such as bird droppings or lichen can shade part of a cell. Because panels are often wired in strings, one badly shaded panel can reduce what others on the same string produce, unless the system has optimisers or microinverters.

Panels most likely to need cleaning

Low-pitch or flat-roof arrays where rain does not run off well
Roofs near trees, which drop sap, pollen and leaves
Homes near farmland, building sites or busy roads
Coastal properties where salt spray dries on the glass
Arrays with pigeons nesting underneath

How to check your panels

Look at them from the ground or an upstairs window, with binoculars if needed
Compare monthly generation figures with the same month last year
Look for patches of droppings, green or white spots of lichen and moss at the frame edges

Never climb onto the roof to check. If output has dropped sharply and the panels look clean, the problem may be the inverter or wiring, and you should contact your installer or an electrician.

Can I clean them myself?

Ground-mounted panels and panels you can reach safely from the ground can be rinsed gently with a hose and soft brush. Avoid pressure washers, abrasive pads, washing-up liquid and strong chemicals, and never go onto the roof. For rooftop panels, a professional pure water clean from the ground is the safer option.