At what time of day and year is it best to clean my solar panels?

The best season is early spring (March-April), just before the sunniest months which account for about 70% of your annual yield. Preferably clean in the early morning or on a cloudy day. If you clean in full sun, the water dries up too quickly causing stains. Moreover, panels in the sun are extremely hot - cold water on a hot panel can cause thermal shock and micro-cracks.

Do it yourself or have it cleaned? From DIY tips and fair prices to professional robot cleaning.

Cleaning solar panels & having them cleaned: the complete guide 2026

Dirty solar panels cost you money. In this guide, we explain when cleaning is necessary, how to do it yourself, and when it's better to call in a professional. With practical tips, honest prices and a free yield calculator.

Calculate your yield loss

Yield loss calculator

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Is solar panel cleaning really necessary?

Short answer: it depends on your situation. For a standard pitched roof (>15° slope) in an unpolluted environment, rain washes away most of the surface dust. In that case, annual cleaning is not necessarily necessary.

BUT, cleaning is called for when:

Bird droppings or tree resin on the panels
Visible haze, green deposit or lichen
Panels lie flat or at low angle (<15°)
Near agriculture, industry, highway or coast
Noticeable drop in yield (check your inverter app)
Panels have not been cleaned for 2+ years

Efficiency loss due to pollution:

Light pollution (particulate matter): 2-5
Moderate pollution (pollen, dust): 5-15%
Heavy pollution (bird droppings, moss, industrial): 15-25%

Source: various international studies + Solarco's own measurements

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How often should you have your solar panels cleaned?

The ideal cleaning frequency varies from one situation to another. Below is an overview based on our experience.

Situation	Main pollution	Frequency	Estimated loss of efficiency
Sloping roof - residential area Residential, urban or suburban environment, slope >15°	Fine dust Pollen Bird droppings	1× per 1-2 years	2-5%
Near industry or motorway Logistics, production, near heavy traffic or industrial estate	Soot Fine dust Industrial precipitation Rubber particles	1-2× per year	5-15%
Flat roof or low pitch Slope <15°, commercial buildings, sheds, stables	Stagnant water Algae Leaves Moss formation	1-2× per year	5-15%
Near agriculture Fields, animal husbandry, stables with ridge ventilation	Ammonia Dust & sand Pollen & resin Bird droppings	1-2× per year	8-20%
Coastal Within 10 km of the coast, exposed to sea breezes	Salt precipitation Sand Algae Seagull poop	1-2× per year	5-15%
Solar farm / large commercial Ground installations, floating installations, >500 panels	Raw material Bird colonies Weeds/shade Sahara sand	2-4× per year	10-25%
After exceptional circumstances Sahara dust, pollen storm, yard activities, prolonged drought	Sahara sand Construction dust Extreme pollen	Ad hoc turn	Variable

Cleaning solar panels yourself: roadmap

⚠️ Safety first: never work on the roof without fall protection. Consider a telescopic brush you use to work from the ground.

Step 1: Choose the right moment

Early morning or cloudy day (prevents thermal shock and rapid drying)

Step 2: Switch off the system

Switch off the inverter before you start

Step 3: Remove loose dirt

Use a soft brush or leaf blower

Step 4: Clean with pure water

Preferably use osmosis or demineralised water → Never: high-pressure cleaner, abrasive sponges, household detergents (Dreft, green soap)

Step 5: Leave to dry streak-free

Osmosis water dries up streak-free by itself. For tap water: dry with soft cloth.

Self-cleaning vs. professional cleaning

An honest comparison so you make the right choice for your situation.

Criterion

Cleaning yourself

Professional - Solarco

Cost

€10 - €50 per turn Material costs only (brush, water, cloth)

From €125 (up to 25 panels) Commercial €2/panel - Industrial €1.50/panel - Incl. inspection and report

Result

Good for light soiling Superficial dust and light soiling. Stubborn dirt (moss, bird droppings) often remains.

Streak-free result 100% osmosis water, no residue. Includes visual inspection + before/after report.

Safety

Risk in roofing work Fall hazard, electrocution risk. Without fall protection or telescopic handle dangerous.

Certified & insured Trained operators with fall protection and aerial platforms. Full liability insurance.

Inspection for damage

No No checking for hot spots, micro-scratches or defective cells. Damage goes unnoticed.

Visual + thermographic Each cleaning including visual inspection and optional thermographic screening for hot spots.

Warranty retention

Uncertain Incorrect products or methods can void the manufacturer's warranty.

In accordance with manufacturer Cleaning method and materials meet the requirements of all major module manufacturers.

Time investment

1 - 3 hours Preparing equipment, collecting ladder, cleaning, clearing. Unfeasible for large installations.

0 hours - we arrange everything Schedule, execute, receive report. You don't have to be there.

Large installations

Impractical Above 25 panels, it becomes too time-consuming, physically demanding and often inaccessible.

Robot: up to 37,500+ panels Battery-powered cleaning robots for solar farms and commercial roofs of all sizes.

Conclusion

Fine for a small pitched roof with light soiling.

Recommended choice

Getting solar panels professionally cleaned

Getting solar panels cleaned doesn't have to be complicated. You request a quote, we schedule a date, and our team does the rest - you don't even have to be there. Afterwards, you will receive a report with before and after photos. No hassles, no surprises, no additional costs.

Our 4-step approach

Thorough pre-inspection

Visual + thermographic check of your installation. We identify hotspots and damage before cleaning.

Robotic cleaning with osmosis water

Our certified cleaning robots operate on battery, without chemicals. Osmosis water dissolves all dirt and leaves no streaks or residue.

Quality control

After cleaning, we recheck each panel. You will receive a detailed report with before and after photos.

Aftercare and Advice

Based on your installation, environment and production data we draw up an optimal cleaning calendar.

Why companies choose Solarco

Professional and environmentally friendly

Solarco uses professional techniques to clean your solar panels, including robotic cleaning systems and osmosis water. This is not only better for your panels, but also better for the environment as no harsh cleaning agents are involved in our solar panel cleaning.

Safety first

We always work according to strict safety guidelines. Our operators are fully certified and trained to work on aerial platforms and roofs. Moreover, we have comprehensive insurance that covers any kind of risk or liability. This allows us to safely clean solar panels.

Innovative cleaning robots

For large solar parks or extensive roof installations, Solarco deploys robot cleaners. These robots run on batteries and are certified by renowned module manufacturers. The robot can quickly and evenly clean large installations of solar panels without damaging the panels.

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Price solar panel cleaning

Across the industry, the cost of professional solar panel cleaning averages between €5 and €10 per panel, depending on accessibility and degree of soiling. At Solar-Co, we charge for private installations up to 25 panels a fixed starting rate of € 125, with a surcharge of €5 for each additional panel. For commercial installations we charge €2 per panel and for industrial projects even just €1.50 per panel. This makes Solarco a price-conscious option for cleaning your solar panels.

In the table opposite, you will find a brief price overview for the different types of cleaning. for a comprehensive overview and more details, please refer to our complete solar panel cleaning price page

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Type of cleaning	Price/panel	Price for 100 solar panels
Private	€5	€500
Commercial Installation	€2	€200
Industrial Installation	€1,5	€150

See the entire price list here

Advantages of professional solar panel cleaning at Solarco

Higher efficiency: Several studies show that cleaning solar panels can provide an efficiency improvement of a few percent to as much as 15%, depending on the degree of contamination.
Longer lifespan: By preventing dirt build-up and hot spots, your entire system will last longer.
Safety and warranty: Many manufacturers recommend professional cleaning to maintain the warranty. Climbing a roof yourself is also not without risk.
Time savings: With the right tools and experience, we can take care of a large installation in a short time, while you yourself spend your precious time on other things.
Sustainable approach: Osmosis water and robotic cleaning minimise the use of harmful chemicals, which is better for the environment as well as for the panels themselves.

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Solar panel cleaning all over Belgium, the Netherlands, Germany and France.

At Solarco, we have carried out an impressive range of cleaning projects: from residential and commercial roofs to large-scale solar parks. Our specialists provided shiny clean panels in towns and villages throughout Flanders, and are active in the rest of Belgium, the Netherlands and even France. Thanks to our mobile cleaning units and years of experience, we guarantee a thorough, sustainable approach every time - regardless of the size or location of your installation.

North Brabant (NL)

25000 modules

West Flanders (BE)

<2000 modules

Limburg (BE)

8000 modules

Brussels (BE)

400 modules

Brussels (BE)

11000 modules

Gelderland (NL)

2000 modules

West Flanders (BE)

550 modules

Antwerp (BE)

<1000 modules

West Flanders (BE)

7500 modules

North Brabant (NL)

20000 modules

Antwerp (BE)

3000 modules

Limburg (BE)

<1000 modules

Frequently asked questions about solar panel cleaning

No, never use a pressure washer. The high water pressure can damage the seals around the cells, affect the anti-reflection coating and cause micro-scratches that you cannot see with the naked eye. Moreover, water can be forced under the panels and into the cabling, resulting in short circuits. Instead, use a soft brush with osmosis water or engage a professional.

Osmosis water is water from which all minerals, lime, salts and impurities have been filtered through a membrane filter. Tap water contains lime and minerals that leave white streaks and stains on the glass when it dries - these deposits reduce light transmission and attract new dirt faster. Osmosis water dries completely streak-free, so your panels stay clean longer and capture maximum sunlight.

It depends on your manufacturer and the method you use. Most module manufacturers explicitly exclude damage caused by improper cleaning from the warranty - think of using pressure washers, abrasives or aggressive chemicals. Professional cleaning with osmosis water and soft brushes does meet the conditions of all major manufacturers. Always keep your cleaning report as proof in case of a warranty claim.

Hotspots are areas on a solar panel that become locally overheated because part of the cell is covered - for example, by stubborn bird droppings, leaves or moss. The covered cell no longer produces energy but has to let the current through from the other cells, causing resistance and heat. Over time, this can permanently damage the cell. Regular cleaning removes the dirt build-up that causes hotspots, and at a professional turn, existing hotspots are detected via thermographic inspection.

No. Household cleaners such as Dreft, green soap, all-purpose cleaner and car shampoo attack the glass's dirt-repellent coating. As a result, dirt actually adheres faster, your efficiency drops and the surface becomes more susceptible to scratches. Abrasives and window scrapers should also be avoided. Only clean your panels with osmosis or demineralised water and a soft brush or sponge.

The best season is the early spring (March-April), just before the sunniest months which account for about 70% of your annual yield. Preferably clean in the early morning or on a cloudy day. If you clean in full sun, the water dries too quickly, causing stains. Moreover, panels in the sun are extremely hot - cold water on a hot panel can cause thermal shock and micro-cracks.

There are three signals: visual - you see a grey haze, spots, bird droppings or green deposits on the glass. Via your monitoring app - a gradual decline in performance ratio compared to comparable days or years. After special circumstances - think a Sahara sandstorm, prolonged drought, or construction work nearby. In doubt? Send us a photo of your installation via the quotation form and we will advise you free of charge and without obligation.