Do solar panels need cleaning?

Yes, most solar panels in the UK need cleaning from time to time. Rain washes off loose dust, but it does not shift bird droppings, lichen or the line of grime that builds up along the bottom edge of each panel, and all of those block light from reaching the cells.

How often depends on where you live. Panels under trees, near farmland or close to a busy road get dirty much faster than panels on an open roof in a quiet street.

Why rain is not enough

Rain runs off the smooth glass and carries some dirt with it. The problem is where that water ends up. It collects along the bottom edge of each panel, where it sits longest and dries, leaving a tide line of grime. Over time that line builds up and starts to shade the bottom row of cells.

Rain also does little to anything stuck to the glass. Bird droppings dry hard. Lichen and moss grip the frames and creep onto the glass edges. Panels on a shallow pitch drain more slowly, so dirt settles more.

What builds up on solar panels

• Bird droppings, which block a cell completely rather than just dimming it
• Lichen and moss on the frames and glass edges, which are stubborn and spread
• Traffic film from main roads, a grey greasy layer that rain does not lift
• Dust and pollen from farmland and trees
• Leaves and sap where panels sit under branches

Bird mess matters most. A cell that is fully covered produces very little, and because cells are wired together, a shaded patch can pull down the output of more than just that one spot.

Signs your panels need a clean

• You can see dirt, bird mess or green edges from the garden or an upstairs window
• Generation in your inverter app is lower than the same month last year, on similar weather
• There is a visible line of grime along the bottom of each panel
• The panels have never been cleaned since they were fitted

Comparing month by month is the most useful check. Sunny and dull years vary, so look for a drop that does not match the weather.

How often should solar panels be cleaned?

For most homes around Keynsham, Bristol and Bath, once a year is enough. Twice a year makes sense if your panels are under trees, near farmland, near a main road, or you get a lot of bird activity. Some panels on open, steep roofs in clean air can go longer, so a yearly look is a sensible habit even if you do not book a clean every time.

We will tell you which applies to your roof at the first visit, rather than selling you a schedule you do not need.

Does cleaning affect the warranty?

Cleaning done properly will not cause a warranty problem. Many panel and inverter warranties expect the array to be maintained, so keeping a record of each clean is worth doing. What can cause damage is the wrong method: walking on the panels, scrubbing with anything abrasive, using strong chemicals or blasting them with a pressure washer. If you are unsure, your installer's handover pack or the panel maker's manual will have cleaning guidance.

Should you clean them yourself?

If you can reach ground-mounted panels or a low single-storey roof safely from the ground, a gentle clean with plain water and a soft brush is fine. Most domestic panels are on a pitched roof, though, and climbing up there is where people get hurt. Our guide on how to clean solar panels on your roof covers what is safe to do yourself.

What a professional clean includes

A proper clean is more than a rinse. When we clean an array, we:

• Survey the panels from the ground for damage, lifted panels and awkward access
• Clean panel by panel with a soft brush and deionised water on a telescopic pole
• Clean the frames and clips as well as the glass
• Rinse with no detergent left behind, so the glass dries clear
• Give you a record of the clean for your warranty or maintenance file

Solar panel cleaning in Bristol and Bath

We clean panels from the ground with deionised water and soft brushes, with no roof walking, no detergent and no pressure washing. See our solar panel cleaning service, or find your area: Bristol, Bath or Keynsham. Call Tom on 0117 279 0045 for a free quote.