Cleaning Solar Panels: When Not to Go on the Roof

For most houses, you should not climb onto the roof to clean solar panels: first check from ground level whether there is persistent dirt, leaf build-up or a genuine drop in output. Light dust and rain marks rarely justify a risky intervention. In Lisbon, where solar radiation is regularly monitored by IPMA, protecting roof safety, access and weatherproofing matters more than making the glass look perfect.

This is only a simple DIY task where safe access has already been designed into the property. If it requires a long ladder, walking on tiles, reaching near cables or working in strong sun, it is no longer a sensible household job.

Contents

1. First, decide whether the panels actually need cleaning
2. What you can do from ground level
3. When gentle cleaning is reasonable
4. Why you should not walk on tiles or panels
5. Call a professional in these situations
6. Set a short routine that avoids unnecessary climbs

First, decide whether the panels actually need cleaning

Look at the modules on a clear day, without judging their condition from one morning’s output. Compare several similar days in the inverter app, if the system has monitoring, and look for visible signs: a strip of leaves caught at the lower frame, heavy dust after nearby works, concentrated bird droppings or new shade from vegetation.

A thin layer of dust is different from a local obstruction. A wet panel may look cleaner while producing less at that moment because of cloud cover. Check IPMA’s observed solar-radiation data before drawing conclusions from one isolated day.

• Record the reading or take a photo before doing anything.
• Check for shade from branches, aerials or laundry.
• Look from the ground for cracks, loose frames or hanging cables.
• Do not touch exposed connectors, boxes or cables.

If output has fallen steadily while the panels look clean, the cause may be the inverter, seasonal shading or the installation itself. Cleaning without a diagnosis may solve nothing.

What you can do from ground level

The safest household maintenance is the kind that does not require walking on the roof. Remove leaves from an accessible gutter only if you can do so without leaning out, standing on a roof or working on a wet surface. You can also prune low vegetation that is beginning to shade the modules, provided this does not involve working at height or near the electrical system.

Binoculars, a phone camera with zoom and inverter readings can help separate maintenance from curiosity. On pitched roofs, a photograph taken from the garden or street, where possible, is safer than resting a ladder on a tile or gutter.

After wind and rain, use the same safe-observation logic outlined in our guide to inspecting a building after heavy wind and rain: look for displaced items, water where it should not be and signs of damage, but do not turn an inspection into an improvised climb.

DGS advises people to avoid roofs and unstable structures, not to use improvised or damaged ladders, and not to work alone on higher-risk repairs. Its safety guidance for repairs after adverse weather remains useful even outside a storm.

When gentle cleaning is reasonable

Cleaning can be reasonable when panels are on a low structure, a technical terrace with suitable guarding, or an area reached through permanent safe access. Even then, check the manufacturer’s manual and installer’s instructions for approved products and methods.

As a general rule, avoid abrasives, harsh scouring pads, metal scrapers and aggressive detergents. The aim is to remove dirt without scratching glass, damaging seals or leaving residue. Use clean water sparingly and a very soft brush made for the task, but only where you can keep both feet on a safe surface.

1. Switch off only what the manual instructs you to switch off; do not improvise electrical operations.
2. Choose a cool morning or late afternoon, with dry footing and no strong wind.
3. Make sure any hose does not create a slipping hazard or reach electrical components.
4. Do not put weight on panels, their structure or roof tiles.
5. Check frames visually and review output again over the following days.

Do not use very cold water on very hot panels. More importantly, do not chase every mark. A safe, watertight roof is worth more than a flawless surface seen at close range.

Why you should not walk on tiles or panels

Tiles can break, shift or become slippery through moisture, dust and moss. Panels are not walkways either: they are built for outdoor exposure, not concentrated body weight. A seemingly quick crossing can damage a tile, fixing, cable or waterproof layer.

Falls are among the most common accidents at home. DGS guidance on preventing accidents at home recommends straightforward fall-prevention measures such as good lighting and reducing hazards; on a roof, those basic measures do not replace professional access, collective protection and suitable equipment.

Using a ladder to reach sideways across a panel is also unsafe. A ladder should be used for designed access, not for working sideways, pulling hoses or applying force with a brush. If one hand must hold the ladder while the other cleans, there is not enough safety margin for the task.

Call a professional in these situations

Contact the installer, a photovoltaic-maintenance company or a roofing professional when the issue goes beyond superficial dirt. A call is particularly important if you find cracked glass, a distorted frame, visibly loose fixings, displaced tiles, water ingress in the loft, unusual smells near the inverter or persistent monitoring warnings.

There is a clear line between visual maintenance and technical intervention. Cables, connectors and inverters belong on the technical side of that line. Do not open boxes, disable protective devices without instructions, or try to dry or seal electrical parts with tape, silicone or filler.

If maintenance coincides with a renovation, record roof access, cable locations and the need to protect the modules in the renovation baseline programme. This prevents scaffolding, painting, roof works or material deliveries being planned without allowing for the existing system.

Set a short routine that avoids unnecessary climbs

A twice-yearly routine is usually more useful than frequent, unfocused cleaning. Inspect at the end of summer, when dust and dry leaves may be more noticeable, and again after the wetter, windier period. Record the date, two or three photos from the same position and any inverter alert.

Include the area around the roof: trees that have grown, nearby gutters full of leaves, climbing plants, a new aerial or neighbouring work that creates substantial dust. IPMA explains that solar exposure includes direct and diffuse radiation; use its solar-radiation information to choose safer times for outdoor observations, without treating that check as a reason to work on the roof at midday.

The practical rule is simple: observe first, clean only where access is genuinely safe, and leave all work at height or near electrical equipment to people who can carry it out with the right methods.

Key takeaways

• Do not climb onto a roof simply to remove light dust from solar panels.
• Compare output across several days and check for shade, leaves or alerts before cleaning.
• Use only permanent access and safe footing; an improvised ladder does not make the job DIY-safe.
• Broken glass, cables, fixings and water ingress require technical support.

If you are renovating a house and need to integrate or protect an existing solar installation, speak with Obra Lisboa before finalising roof, access and external-work decisions.

Sources and further reading

• DGS guidance on preventing accidents at home
• safety guidance for repairs after adverse weather
• IPMA’s observed solar-radiation data
• solar-radiation information

Editorial image; it does not depict an Obra Lisboa project.