How Often Should Solar Panels Be Cleaned?

Why rain is not always enough

Rainwater runs down the glass and carries loose dust with it, but it slows as it reaches the lower frame. Fine dirt settles there and builds into a line that rain cannot lift. On shallow-pitched panels, water and dirt linger longer still.

Sticky deposits like bird droppings and tree sap bond to glass and dry hard, so a shower simply runs around them.

What speeds up soiling

Panels near trees collect pollen, sap and leaves. Homes close to farmland see more dust at harvest. Houses near busy roads collect traffic grime. Coastal properties can build up salt. Roofs that are popular with pigeons or gulls collect droppings far faster than others.

A roof facing north or shaded part of the day also stays damp longer, which helps moss and algae creep from the tiles onto the panel edges.

Signs it is time for a clean

From the ground, look for visible streaks, patches of droppings, a green or brown line along the bottom frame, or moss on the frame edges. Compare your generation figures from the inverter or app with the same month in earlier years, allowing for weather differences.

A noticeable, unexplained drop is worth investigating, though it can also point to an electrical fault that cleaning will not solve.

A rough pattern for most homes

Many households find that an occasional clean, perhaps every year or two, keeps panels looking tidy, while panels near trees, farms or busy bird roosts may benefit from more frequent attention. Others in open, clean settings rarely need cleaning at all.

Rather than booking on a fixed schedule, it is usually better to look at the panels and the figures, then decide.

Combining with roof and gutter work

Moss on the roof tiles can spread onto panel frames and choke the gaps beneath them. If the roof is due for moss removal, cleaning the panels during the same visit is efficient. Read our solar panels and roof moss guide for how the two interact.

Gutters below panels can also fill with debris that washes off the glass, so it makes sense to check them at the same time.

Checking warranties and guidance

Some panel manufacturers and installers give guidance on cleaning methods and products. It is worth checking your paperwork, since harsh chemicals or abrasive tools may not be recommended.

We use gentle, low-pressure methods suited to glass panels; the detail for your system is confirmed at quote stage.

Ground-mounted and garden arrays

Panels mounted on the ground or on low garden structures pick up more splash, grass cuttings, soil and pollen than roof panels. They are also easier to reach, so owners often keep them clean themselves between occasional professional visits.

Our DIY cleaning guide covers safe methods for low panels.

Shallow-pitch and flat roof panels

Panels on flat roofs or shallow pitches shed water slowly, so dirt and moss settle more readily, particularly along the lower frame. These arrays often need attention more often than steep roof panels in the same area.

If panels sit flat on a roof with no tilt at all, standing water can leave a ring of grime once it evaporates.

Keeping a simple record

Writing down when panels were last cleaned, along with monthly generation figures, makes it much easier to judge when the next clean is due. Over a couple of years, you will see how quickly your panels soil and whether cleaning makes a visible difference.

Most monitoring apps store figures, so it is mainly a case of noting the cleaning dates.

Getting a quote

Tell us how many panels you have, where they are on the roof and whether birds nest underneath. Our solar panel cleaning service page explains how a visit works, and quotes are free.