The short answer
Yes, when the panels are dirty. Dust, salt and bird droppings block light from reaching the cells, so output drops until the panels are cleaned. On panels that are already fairly clean the difference is small. The reliable way to know is to compare your own inverter readings on two similar clear days, before and after a clean.
The short answer
Cleaning increases output when the panels are dirty. Solar cells can only turn into electricity the light that actually reaches them, and a layer of dust, salt or bird droppings on the glass blocks some of it. Remove the layer and the light gets through again.
If your panels are already fairly clean, a clean will make little difference. So the real question is not whether cleaning works, but whether your panels are dirty enough for it to matter. That is something you can check yourself.
What dirties solar panels in Malta and Gozo
Panels here deal with more than rain and leaves:
- Dust through the dry summer. Months with little or no rain mean dust builds up exactly when panels should be producing the most, and rain rarely cleans panels properly when it does come.
- Saharan dust and red rain. The xlokk brings fine dust from North Africa a few times a year. A light shower turns it into a muddy film that dries hard in the sun. Our guide to red rain and Saharan dust explains what it does to panels.
- Salt near the coast. Homes on the seafront, and roofs exposed to the majjistral, collect a fine salt film that also traps dust.
- Building and quarry dust. Construction next door, or a quarry or busy road nearby, can coat panels in limestone dust within weeks.
- Bird droppings. Pigeons and gulls perch on raised frames and parapets, and droppings bake onto the glass.
Panels on low frames on flat Maltese roofs tend to suffer more, because a shallow tilt sheds water and dirt less well. You will often see a dirty band along the bottom edge.
Why bird droppings matter more than dust
A thin, even layer of dust reduces the light reaching every cell a little. A bird dropping blocks part of one cell almost completely.
Cells in a panel are wired together in strings. When one cell is heavily shaded, it can hold back the cells around it, so a small dropping can cost more output than its size suggests. Over time, a heavily shaded spot can also heat up more than the rest of the panel. That is why droppings are worth removing promptly, even when the rest of the panel looks clean.
How to check the difference on your own system
You do not need special equipment. Most inverters come with an app or online dashboard that shows how much your system produces each day.
- Pick two similar days. Both should be clear and sunny, ideally close together, so the sun is at a similar height. A hazy or cloudy day gives misleading readings.
- Note the daily total before cleaning. Write down the total energy for a clear day, in kWh.
- Clean the panels, or have them cleaned.
- Note the daily total after cleaning, on another clear day as close as possible to the first.
- Compare. A clear jump means the panels were dirty enough to matter. Little or no change means they were not, or something else is going on.
It also helps to keep a note of your production on clear days through the year. If output on sunny days slowly drifts down over weeks, and nothing else has changed, dirt is the likely cause.
When cleaning will not help
If your output has dropped and the panels look clean, the cause is probably something else:
- New shading from a building going up next door, a new water tank, an extra floor or a satellite dish.
- Heat. Panels produce less when they are very hot, so a scorching August afternoon can look worse than a cool, clear April day.
- An inverter fault, a warning light or an error message in the app.
- A tripped breaker or isolator.
Electrical checks are a job for your installer or a licensed electrician, not a cleaner. Our guide on why solar output is low walks through each cause.
When to clean for the biggest benefit in Malta
- At the end of the dry summer, usually September or October, when months of dust have built up.
- After a heavy red rain or Saharan dust episode, once the haze has cleared.
- In spring, before the longest days, so panels are clean when they produce the most.
For most homes, once or twice a year is enough, with extra cleans for seafront roofs, roofs near building sites or fields, and roofs with a bird problem. Our guide on how often to clean solar panels in Malta goes into more detail.
Cleaning safely
If you clean the panels yourself:
- Clean early in the morning, when the panels are cool.
- Use plenty of water and a soft brush. Purified water dries without spots.
- Never use a pressure washer, scouring pads or strong detergents.
- Never walk on panels or climb raised frames.
- Follow your panel manufacturer’s cleaning guidance, which is usually in the manual.
Clean the wrong way and you risk damage your warranty may not cover. See does cleaning solar panels void the warranty.
When to call a professional
A professional clean makes sense when panels are on raised frames or over a roof washroom, when the roof has low parapets or awkward access, when there are a lot of panels, or when there is heavy, baked-on dirt or droppings. A good cleaner will also tell you if they notice cracked glass, loose fixings or damaged cables, so you can call your installer.
clear.mt arranges solar panel cleaning across Malta and Gozo. Tell us roughly how many panels you have and send a photo of the roof for a free quote.