The short answer
Yes. Solar panels need cleaning because dirt, bird droppings, lichen and moss block the light the cells need, and rain doesn’t wash them off. As a guide, commercial panels should be cleaned about once a year, and more often on dirty sites. Ground-mounted arrays usually get dirtier than panels on a roof.
So do solar panels need cleaning? If your business has invested in solar on a roof, a car park canopy or a field, the panels are there to cut your energy bills. When dirt builds up on the glass, less light reaches the cells and they generate less power, often without anyone noticing. This guide explains why panels get dirty, how often they should be cleaned, and what to look for in a cleaning contractor.
Do solar panels need cleaning if it rains?
Rain helps, but it doesn’t keep panels clean. It runs off loose dust, but it leaves behind the things that cause the most shading:
- Bird droppings bake onto the glass and block the light to whole cells, which pulls down the output of the panel.
- Lichen and moss grow from the frame edges, especially on panels that sit in shade or near trees.
- Dust, pollen and traffic film build up in a thin, greasy layer that rain smears rather than shifts.
- Dirt at the bottom edge: on panels at a low tilt, rainwater carries dirt down and leaves it in a line along the frame.
Businesses near farmland, busy roads, building sites or industrial units tend to see the most build-up. So do sites with lots of birds, such as anywhere near water, warehouses with flat roofs, and fields with trees around the edge.
How often should solar panels be cleaned?
As a guide, once a year. That’s enough for many business roofs. But every site is different, and some need cleaning more often:
| Type of site | As a guide | Why |
|---|---|---|
| Business roof, clean area | Once a year | Mostly dust and pollen, washed partly by rain |
| Roof near roads, farms or industry | More than once a year | Traffic film, dust and agricultural dirt build up faster |
| Ground-mounted arrays and solar farms | Often more than once a year | Closer to soil, crops, livestock and birds, so they get dirtier |
| Sites with lots of birds | More often | Droppings cause the worst shading |
For example, one of our clients, a business with a brand-new head office, has its roof panels cleaned every three months. Others are fine with a yearly clean. We’ll look at your panels and recommend a schedule for your site.
Solar panel cleaning is easy to add to your regular window cleaning visit, so the panels get cleaned without an extra call-out. How often should commercial windows be cleaned?
Signs your panels need a clean
- Your monitoring app or inverter shows lower output than the same month last year, on similar sunny days.
- You can see droppings, a grey film, or green growth around the frames.
- Dirt has collected in a line along the bottom edge of each panel.
- The panels haven’t been cleaned since they were installed.
Lower output can also be caused by a fault, so if the panels look clean and output has still dropped, speak to your installer or maintenance company.
Roof-mounted and ground-mounted panels
Ground-mounted arrays and solar farms are the easiest to clean well, because the panels can be reached safely from the ground. On a ground-mounted site we can clean around 300 panels a day, depending on the layout. We follow your site rules and inductions, and plan the work around access, gates and anything else happening on site.
Roof-mounted panels take longer, because the work is at height and access has to be planned. We clean roof panels where they can be reached safely, and we’ll ask about the roof, the panels and access when you request a quote. Never send your own staff onto a roof to clean panels. Work at height needs a risk assessment and the right equipment. What safety paperwork to ask a contractor for.
How we clean solar panels
We clean solar panels with de-ionised (pure) water and soft brushes only. Pure water has had its minerals removed, so it dries without leaving spots or a film on the glass, and no chemicals or detergents are needed. Nothing harmful runs off onto the roof, the ground or the land around a solar farm.
Some panel manufacturers set out in their warranty terms how panels may be cleaned, so check yours before anyone uses a pressure washer, harsh chemicals or abrasive pads on the glass. Soft brushes and pure water are the gentle option.
Every operator holds at least £2 million of public liability insurance, and higher cover is available for larger sites. Your quote comes with our insurance documents, and once you’ve accepted it we can prepare a free risk assessment and method statement for your site. We already clean solar panels for businesses across South Yorkshire, including AESSeal and Memoria. Commercial solar panel cleaning.
What to tell us when you ask for a quote
- Roughly how many panels you have, and whether they’re on a roof or on the ground.
- Where the site is, and how we get to the panels (roof access, gates, keys).
- When they were last cleaned, if you know.
- Any site rules, inductions or working hours we need to follow.
- A few photos of the panels, if you can take them safely.
Tick solar panel cleaning on the quote form. We reply within 2 hours during office hours. We also clean gutters and cladding for any commercial building. Our commercial cleaning services.
Questions
Can rain clean solar panels?
Not properly. Rain washes off some loose dust, but bird droppings, lichen, moss and traffic film stay on the glass, and on low-tilt panels rain leaves a line of dirt along the bottom edge.
How often should solar panels be cleaned?
As a guide, once a year for most business roofs. Ground-mounted arrays and sites near farms, roads or lots of birds may need cleaning more often. We’ll recommend a schedule for your site.
Do you use chemicals to clean solar panels?
No. We use de-ionised water and soft brushes only, so no residue is left on the glass and nothing harmful runs off.
Do you clean solar farms?
Yes. Ground-mounted arrays are our preference. We can clean around 300 panels a day on a ground-mounted site, and we follow your site rules and inductions.
Can you clean our solar panels on the same visit as the windows?
Yes. Solar panel cleaning is easy to add to a regular window cleaning visit. Solar panel cleaning.
Photo: Neville Hawkins on Pexels.
