The short answer
Soak droppings with plenty of clean water until they soften, lift them off with a soft brush, then rinse. Never scrape them or use abrasive pads or strong cleaners. Remove them promptly, because a dropping blocks part of a cell completely and can affect the output of the whole panel. If pigeons are nesting under the panels, have the edges bird-proofed by your installer or a specialist.
Why droppings matter more than dust
A layer of dust reduces the light reaching every cell a little. A bird dropping is different: it blocks part of a cell almost completely.
Solar cells are wired together in strings, so the current through a string is limited by its weakest cells. One heavily shaded cell can hold back the cells around it. That is why a few droppings can cost more output than their size suggests.
There is a longer-term risk too. A cell that is heavily shaded while the rest of the panel is in full sun can run hotter than its neighbours, known as a hot spot. Left for long periods, hot spots can damage the panel. Removing droppings promptly avoids the problem.
How to remove droppings safely
Only do this if you can reach the panels safely from the roof without climbing onto frames or panels. If not, leave it to a professional.
- Choose a cool time. Early morning is best, when the panels are cool. Cold water on hot glass is never a good idea.
- Soak the dropping. Wet it with plenty of clean water and leave it to soften for a few minutes. Dried droppings can take several soakings.
- Lift it off gently. Use a soft brush or a soft sponge, working in straight strokes. Let the water do the work rather than pressure.
- Rinse the whole area. Rinse well so no residue is left to dry on the glass. Purified water dries without spots if you have access to it.
- Check the result from a safe spot once the glass has dried.
What not to use
- No scrapers, blades or scouring pads. They scratch the glass and its anti-reflective coating.
- No pressure washers. High pressure can damage seals and coatings.
- No strong detergents, solvents or ammonia-based cleaners.
- No walking on panels, and no climbing raised frames.
Always check your panel manufacturer’s cleaning guidance, usually in the manual, before using anything other than water and a soft brush.
Why pigeons nest under panels on Maltese roofs
Pigeons and other birds are attracted to rooftop solar for simple reasons:
- Shelter. The gap under a panel is shaded, out of the wind and hard for predators to reach.
- Raised frames. Flat Maltese roofs often have panels on raised frames, sometimes over a roof washroom or next to water tanks, which leaves plenty of sheltered space underneath.
- Food nearby. Bins, balconies where birds are fed, and busy streets keep them close.
Once birds start nesting, the problem grows quickly: more droppings on the panels, nesting material and debris collecting underneath, and noise and mess on the roof.
What nesting does to your system
- More droppings on and around the panels.
- Debris under the panels, such as twigs, feathers and old nests, which blocks airflow and can trap moisture.
- Risk to cables. Birds and nesting material near cables and connectors are not good for them. Any damage to cables is a job for your installer or an electrician.
- Mess on the roof, which makes access for cleaning and maintenance harder.
How to prevent it
Bird-proofing mesh
The most effective long-term fix is mesh fitted around the edges of the array, closing the gap between the panels and the roof so birds cannot get underneath. It is usually clipped to the panel frames rather than drilled, and it should be fitted by your installer or a specialist bird-proofing company so the panels, cables and warranty are not affected.
If birds are already nesting, the space should be cleared and cleaned before the mesh goes on. If there is an active nest with eggs or chicks, ask the specialist for advice before removing it.
Keep the roof uninviting
- Clear the roof of old items, timber and clutter that give birds shelter. For bigger jobs, a house and garage clearance can clear a cluttered roof or washroom in one go.
- Do not leave food out, and keep bins closed.
- Check under the panels a couple of times a year for signs of nesting.
Use humane methods only. The aim is to stop birds settling, not to harm them.
How often to check and clean
Roofs with regular bird activity are worth checking every few weeks, with droppings spot-cleaned as they appear and a full clean once or twice a year. Most homes without a bird problem only need a full clean once or twice a year, at the end of the dry summer and in spring. See our guide on how often to clean solar panels in Malta.
If your output has dropped and you are not sure why, our guide on why solar output is low walks through the other causes.
When to call a professional
Call a professional cleaner when droppings have baked on, when panels are on raised frames or over a washroom, when the roof has low parapets, or when there is a lot of mess under and around the panels. A cleaner will also tell you if they notice cracked glass, damaged cables or signs of nesting, so you can call your installer about bird-proofing.
clear.mt arranges solar panel cleaning, including bird dropping removal, across Malta and Gozo. Send a photo of the roof and a rough panel count for a free quote.