Do solar panels need cleaning?

Solar panels need less cleaning than most people expect, but they do need some. The Energy Saving Trust says rain usually keeps rooftop panels fairly clean, so routine cleaning is not essential, and suggests checking them every one to two years. A clean becomes worthwhile when something builds up that rain will not shift, such as bird droppings, lichen, leaves or a film of salt.

This guide explains what to look for, why coastal homes tend to need more attention, and how to clean panels without causing damage.

What builds up on panels

• Bird droppings. Gulls are the main offenders around Torbay. A dropping that sits on the glass blocks the light to the cells under it.
• Lichen and moss. These grow along the bottom edge of the panels and the frames, where water and dirt collect.
• Leaves and pine needles, especially where trees overhang the roof.
• Salt film. Properties close to the sea pick up a thin layer of salt from spray carried on the wind. Rain moves it around but does not always wash it off.
• Dust and pollen, which build up in dry spells and in spring.

Because the cells in a panel are connected, shading on part of a panel can reduce what the whole panel produces, not just the dirty corner. That is why a few large droppings can matter more than an even layer of dust.

Signs your panels could do with a clean

• You can see droppings, green edges or a dull film from the ground or an upstairs window
• Generation on your app or inverter is lower than the same month last year, with similar weather
• There are trees close to the roof, or gulls regularly sit on it
• You live within sight of the sea

Comparing like with like matters. Solar output naturally drops in the winter months because the days are shorter and the sun is lower, so a fall in November against July is normal. A fall against the previous November is more telling.

How panels should be cleaned

The Energy Saving Trust's guidance is to use plain water with a soft brush or sponge, avoid pressure washers, which can damage seals and wiring, and avoid washing up liquid and other products that can leave a residue. It also advises cleaning from the ground where possible and never standing on the panels.

That is how we clean them. Pure water, filtered so it has no minerals in it, goes through a telescopic pole with a soft brush, and everything is done from the ground. Pure water dries without spots, the same reason it works so well on windows. We explain that in more detail in how to clean windows streak free. No detergent goes on the glass and nobody walks on the roof.

If you want to try it yourself, check your installer's or manufacturer's guidance first, because some warranties include conditions about cleaning and servicing. Do not get on the roof or lean a ladder on the panels.

Is winter a good time to clean them?

It can be. Output is lower in winter anyway, so a clean then has less immediate effect than one in spring. But autumn leaves and gull mess left over winter can be harder to shift by March, and lichen keeps growing in the damp. A clean in late autumn or early spring sets the panels up for the longer days. The Energy Saving Trust also suggests cleaning in cool conditions, such as an overcast day, because water evaporates too quickly from hot panels and can leave marks.

How often

Once a year is plenty for most homes. Twice a year can be worth it close to the sea, under trees, or where gulls are a regular problem. Ground-mounted panels tend to get dirtier than roof panels and may need more.

Solar panel cleaning in Torbay and Exeter

AbraClean cleans solar panels with pure water from the ground across Torbay, South Devon and Exeter. See our solar panel cleaning service, or add it to your window cleaning visit. Areas include Brixham, Torquay and Exeter. Call or text Mark on 07901 563000 for a free quote.