If you live in Andalusia, Murcia or the Valencia region, you know the scene: the sky turns orange, your car wakes up covered in reddish dust and, if it rains, what falls is mud. That same layer settles on your solar panels and robs them of light in precisely the sunniest parts of Spain.
The good news is that cleaning your solar panels is simple and cheap if you know when to do it and what to avoid. In this guide we explain how often to clean them depending on where you live, what to do after a calima (Saharan dust) episode and how to do it step by step without damaging the panels or voiding the warranty.
In short: in most of Andalusia and the Levante it is enough to clean your solar panels twice a year, and up to three or four times in the driest areas (Almería, Murcia, southern Alicante) or on the seafront. On top of that, add an extra clean after every strong calima or mud rain episode. All you need is water, a soft brush and cool panels: first thing in the morning or at dusk.
Why dust and calima reduce the output of your solar panels
A solar panel produces electricity in proportion to the light that reaches its cells. Anything that gets between the sun and the glass cuts production, and calima does this in two different ways.
While the episode lasts, the dust in the air filters the radiation before it reaches the roof. During the great calima of March 2022, a study by the University of Jaén and Sapienza University of Rome calculated that Spain’s photovoltaic output halved for more than two weeks, dropping by 80% on the worst day. There is nothing you can do about that: you just have to wait for the sky to clear.
When the episode ends, the dust that has settled stays on the panels. This is where you can act. That layer works like a permanent filter and adds to the usual dirt in our area:
- Dust from dirt tracks, building works and farmland, especially during long summers without rain.
- Salt spray, in homes near the sea on the Costa del Sol, the Costa Tropical, Almería, the Mar Menor or the Costa Blanca.
- Pollen, leaves and bird droppings, which can also create hot spots on the panel.
- Mud rain, which dries into a crust that sticks far harder than dry dust.
The effect builds up when it doesn’t rain. In a year-long trial in southern Spain, uncleaned modules lost up to 19% of their power after two dry summer months, while no losses were recorded during rainy periods. They were concentrator modules, which are more sensitive to dirt than residential panels, but the pattern is the same: the longer it goes without rain, the more production is lost along the way.
How often to clean solar panels depending on the area
There is no single figure: it depends on how much it rains where you live, how close you are to the sea and what surrounds your roof. As a starting point, these are the frequencies we recommend for each area.
| Area | Cleans per year | Why |
|---|---|---|
| Costa del Sol and the coast of Málaga, Granada and Cádiz | 2 | Very dry summers and frequent calima; salt spray adds up in homes close to the sea |
| Inland Andalusia (Seville, Córdoba, Jaén, Granada) | 2, or 3 next to dirt tracks and farms | Four or five months with almost no rain and lots of dust from the fields |
| Almería and the Region of Murcia | 3 or 4 | Semi-arid climate: it barely rains enough to wash the panels |
| Southern Alicante (Vega Baja, Elche, Torrevieja) | 3 | Same conditions as Murcia, with salt spray on the coast |
| Valencia, Castellón and northern Alicante | 2 | More rain, but concentrated in autumn; summer is just as dry |
| Seafront properties, in any area | A rinse with water every 2 or 3 months | Salt forms a film that dust turns into a crust |
If you are going to clean twice a year, the best times are late spring, once the season’s calima episodes are over and the months of highest production begin, and late summer, to remove the dust built up during the dry spell.
If you live on the Costa del Sol, you can find more information about our solar panels in Málaga, solar panels in Marbella and solar panels in Estepona.
There are three cases in which you should clean more often:
- Panels with a low tilt (less than 10 or 15 degrees), common on flat roofs: rain washes the dirt away less effectively and water collects on the bottom edge.
- Building works or earthworks near your home.
- Trees or birds above the roof: droppings are not washed away by rain and should be removed as soon as possible.
What to do after a calima or mud rain episode
Calima reaches the south and east of the peninsula several times a year, most often between late winter and spring and again in summer. When it happens, follow this order:
- Wait until it is over. Cleaning in the middle of a calima is pointless: the dust settles again within hours. Check the AEMET dust forecast to know when it will clear.
- Look at the sky before grabbing the hose. If the dust is dry and clean rain is forecast within two or three days, you can let it do part of the job.
- If there has been mud rain, don’t wait. Dried mud sticks to the glass and every sunny day hardens it further. Clean it as soon as the episode has passed.
- Never remove it dry. Saharan dust is mineral and abrasive: wiping it with a cloth or a dry brush scratches the glass’s anti-reflective coating. First plenty of water to wash it off, then the brush.
- Check the result in your inverter app on the next clear day. If production does not return to its usual level, there is still dirt stuck on or there is another problem.
How to clean solar panels step by step
You need a hose, a soft-bristle brush or a microfibre mop on a telescopic pole and, at most, a little neutral soap.
- Think about your safety first. Clean from the ground, a terrace or a stable ladder, using the pole. Do not climb onto a pitched roof without a safety line and never step on the panels.
- Choose the right time. First thing in the morning or at dusk, when the panels are cool. At midday the glass easily exceeds 60 °C: the water evaporates instantly, leaves marks and the temperature contrast can damage it.
- Check before wetting. If you see broken glass, a loose frame or an exposed cable, do not clean and contact your installer.
- Rinse with low-pressure water. The normal flow from a garden hose washes off loose dust without scrubbing. Avoid aiming it at the inverter, the electrical panel and the connectors on the back.
- Scrub gently, from top to bottom. With the brush or mop well soaked. If there is grease or droppings, add a few drops of neutral soap to the water and let it soften the stain before going over it again.
- Rinse with plenty of water until no foam is left: soap residue traps new dust.
- Watch out for limescale. The water on the Costa del Sol, in Murcia and in much of the Valencia region is hard and leaves white marks as it dries. Do the final rinse with demineralised water or remove the water with a rubber squeegee.
A home installation of 8 to 12 panels can be cleaned in less than half an hour.
What not to do when cleaning solar panels
Most cleaning damage comes from five mistakes. Avoid them, because manufacturers usually exclude damage caused by improper cleaning from the warranty.
- Pressure washers. The jet can damage the frame seals, force water in and cause micro-cracks in the cells.
- Harsh products. No bleach, ammonia, solvents, degreasers or glass cleaners containing alcohol: they attack the anti-reflective coating and the seals.
- Scourers, blades or hard brushes. They scratch the glass, and scratched glass loses production for good.
- Cleaning in full sun. Cold water on a very hot panel is an unnecessary thermal shock.
- Dry cleaning. Especially after a calima: it is like rubbing them with fine sandpaper.
How to tell if your solar panels need cleaning
There is no need to climb onto the roof: your inverter app will tell you. Compare the production of a clear day with that of another clear day at the same time of year, or with the same month of the previous year. A sustained drop of 5% to 10% with no new shading or fault alerts is almost always dirt.
To the naked eye, these signs mean it is time to clean:
- A dull or reddish film that takes the shine off the glass.
- A strip of dirt built up along the bottom edge of each panel.
- Bird droppings, leaves or localised stains.
- White rings of limescale or salt.
If you clean and production does not recover, the problem is not dust. It could be shading, an optimiser, a connector or the inverter itself, and it is worth having a technician check it.
When professional cleaning is worth it
Call a professional if your panels are on a pitched or hard-to-reach roof, if the installation is large (residential communities, industrial buildings, shops), if there is encrusted mud or limescale that water does not remove, or if the water in your area is very hard. A specialist team works with demineralised water, approved brushes and safety measures for working at height, and uses the visit to check the mountings, wiring and connectors.
Annual solar panel maintenance with SolQuality
At SolQuality, in addition to the installation of solar panels, we offer an annual maintenance service for photovoltaic installations from €185 + VAT per year, designed to guarantee the performance, safety and durability of your installation. It includes:
- A full annual inspection of the photovoltaic installation.
- One solar panel cleaning.
- Up to two visits a year for quick system reconfigurations, replacement or adjustment of small parts and minor changes.
The base price covers installations of up to 8 panels. Beyond that, €10 is added for each additional panel: an installation of 12 panels, for example, would be €225 + VAT per year. The final amount may be adjusted depending on the type of installation and its characteristics.
That professional cleaning covers one of the two we recommend each year. The other one, and the touch-ups after a calima, you can do yourself by following the steps in this guide.
We provide the service throughout Andalusia and the Region of Murcia. If you would like to sign up for maintenance, or your installation is producing less than it should and you don’t know why, get in touch and we will check it.
Frequently asked questions about cleaning solar panels
Does rain clean solar panels?
Only partly. Heavy, clean rain washes off loose dust, but it does not remove droppings, salt or dried mud. And the light showers that follow a calima do the opposite: they leave the panels dirtier than before.
How much production is lost with dirty panels?
It depends on how long they have gone without washing. With light dirt the loss is a few percentage points; after a whole summer without rain or a mud rain episode it can exceed 10%. The reliable way to find out is to compare your production before and after cleaning. That lost production also lengthens the period in which solar panels pay for themselves.
Can I clean solar panels with a Kärcher or pressure washer?
It is not recommended. The pressure can damage the seals and the cells, and it is one of the usual reasons for the warranty being voided. The normal pressure of a garden hose is enough.
What product should I use to clean solar panels?
Water. If there is stuck-on dirt, add a little neutral soap and rinse well. No special products are needed, and harsh household cleaners should not be used.
Is it better to clean the panels in the morning or in the afternoon?
Either, as long as the panel is cool. First thing in the morning has the advantage that the dew will already have softened the dirt.
Do I have to switch off the installation to clean it?
For a gentle wash with the panels in good condition it is not usually necessary, but always follow your manufacturer’s manual. Never clean if you see broken glass or damaged cables.
How often should solar panels be cleaned in Málaga and on the Costa del Sol?
Twice a year, in late spring and late summer, plus an extra clean after every strong calima or mud rain episode. If you live on the seafront, add a rinse with water every two or three months to remove the salt.
How much does solar panel maintenance and cleaning cost?
SolQuality’s annual maintenance starts at €185 + VAT per year for installations of up to 8 panels, with a €10 supplement for each additional panel. It includes a full inspection of the installation, one panel cleaning and up to two visits for adjustments and minor changes. The price may vary depending on the characteristics of each installation.
You will find more answers in our frequently asked questions about solar panels.
