FAQFrequently asked questions

For residential roofs, Solarco charges a fixed starting rate; as a guide, the market price is €5 to €10 per panel. On larger commercial and industrial installations, economies of scale bring the price down to around €0.40 to €2 per panel. The exact cost depends on access, the number of panels and how dirty they are, so request a free, no-obligation tailored quote.

The price mainly depends on how easy the roof is to access, the type of installation and the number of panels. The larger the installation, the lower the price per panel: from roughly €5 to €10 per panel on small residential roofs to €0.40 to €2 per panel on large commercial and industrial installations. The level of soiling and the pitch of the roof also play a part.

Yes. A clean typically pays for itself within a year. A dirty panel can produce 5 to 15% less, and even more when heavily soiled. On larger installations, that lost yield quickly adds up to many times the cost of cleaning. Use our yield loss calculator to work out your own payback period.

For a large ground-mounted solar park, cleaning costs roughly €0.40 to €0.90 per panel per visit. Including vegetation management and visual and thermographic inspections, total annual maintenance for a park of around 10,000 panels comes to approximately €14,000 to €18,000. Without maintenance, yield losses can reach 10 to 15% a year, which is usually many times that cost.

On commercial installations, soiling can go unnoticed and cause a 5 to 15% loss in yield each year. On a commercial roof, that lost output can run to thousands of euros a year, against a far lower cleaning cost. In practice, this means payback periods are often between 1 and 5 months.

For most residential installations in Belgium and the Netherlands, one clean a year is enough. In dusty or demanding environments, such as near farms, industry, busy roads, the coast, or on flat roofs, twice a year is advisable. Flat and gently pitched roofs get dirty faster than steep ones, because rain washes less of the dirt away.

The ideal time is early spring (March to April), after the winter and pollen season and just before the months of peak solar yield. Clean early in the morning or on an overcast day if you can: on hot panels, water dries too quickly and leaves marks. Never clean in full sun.

Commercial and industrial installations are generally cleaned at least once or twice a year, depending on how much pollution there is in the surrounding area. Ground-mounted solar parks often need two to four cleans a year. Near heavy industry, motorways or intensive farming, more frequent cleaning is advisable.

Light dirt on an easily accessible roof can be removed yourself with pure water and a soft brush. High, steep or large roofs are best left to professionals: they work from the ground or with fall protection, use the right equipment and spot defects straight away. If you have any doubts about your warranty or safety, a professional clean is the safest option.

Cleaning panels on a roof yourself carries a considerable risk of falling and of electrocution, and you should never walk on the panels themselves, as this can easily cause micro-cracks and hotspots. Solarco's operators are certified for working at height, use fall protection and are fully insured. Cleaning panels the wrong way can also put your manufacturer's warranty at risk.

Avoid pressure washers, hard or abrasive brushes, steel wool and household cleaning products, as they damage the coating and seals. Never clean the panels dry (this creates static and scratches) and never in full sun, because the water evaporates too quickly and leaves streaks. Don't use cold water on hot panels, to prevent thermal shock and micro-cracks.

Under normal conditions, dirty panels lose 5 to 10% of their yield on average, rising to 20% or more with heavy soiling such as moss, bird droppings or a continuous layer of dust or sand. Localised dirt is especially harmful because it can cause a hotspot that drags down the output of the whole panel. Regular cleaning keeps yield where it should be.

Bird droppings are acidic and cause permanent damage over time, and they also cast hard, concentrated shade over a single cell. This can cause a local yield loss of around 20% and trigger the bypass diodes, leading to hotspots and faster degradation. The damage is far greater than such a small mark would suggest, so remove bird droppings promptly.

The three biggest levers are regular cleaning (which can easily add a few per cent to more than 10% in output), a periodic thermographic inspection to detect faulty cells and hotspots, and making sure the panels don't become shaded or overgrown. An annual maintenance visit combines all three and keeps your installation performing at its best.

No, but it is sometimes oversold. It's true that rain removes loose dust, so cleaning more often than necessary makes little sense. However, what rain does not wash away (moss, lichen, bird droppings, pollen and Saharan sand) can reduce yield by 15% or more. The sensible approach is to have your installation checked every year and only clean it when needed.

In Belgium and the Netherlands, solar panels produce on average between 850 and 1,100 kWh per kWp per year. A typical 4 kWp household system therefore generates around 3,400 to 4,400 kWh a year, a substantial saving on your energy bill. Actual output depends on orientation, tilt angle, shading and how dirty the panels are.

Output depends on orientation, tilt angle, temperature, inverter quality and how dirty the panels are. A south-facing array at around 35° is optimal; east- or west-facing panels produce 10 to 20% less. On top of that, soiling can easily cost 5 to 10% of annual yield, which regular cleaning avoids.

Lichen is a biological layer of algae, fungi and mosses that bonds to the glass, reduces the amount of light reaching the cells and increases the risk of hotspots and micro-cracks. Never remove it yourself with a pressure washer, abrasives or household products, as this causes permanent damage. Professional removal is carried out after an inspection, using soft brushes and pure water, with the right safety measures in place.

Together with pollen and soot, Saharan sand forms a stubborn crust that rain does not wash away. It typically reduces yield by 2 to 5%, and by 8 to 10% or more where layers are thick and uneven. Remove it using low-pressure methods: suitable non-abrasive brushes or robots and pure water, without pressure washers or harsh chemicals. Cleaning is advisable as soon as you can still see sand on the panels after rain.

Usually not: panels are tilted and warm up, so snow slides off on its own, and a thin layer that melts within a day rarely justifies the effort. If the panels stay covered for several days, or on flat roofs, removing the snow can be worthwhile. But never climb onto a snow-covered roof yourself: the risk of falling far outweighs a few days' worth of output.

Use a soft telescopic brush or a snow rake with a rubber or foam edge and sweep gently, ideally from the ground. Never use a metal scraper, salt or chemical de-icers, and don't use a pressure washer in freezing conditions, as thermal shock can crack the cells. For flat roofs, large installations or work at height, it's best to call in a professional team.

An inspection includes a visual check of the glass, frames, cabling, clamps and mounting hardware, backed up by measurements such as DC voltage, an inverter check and fault code diagnostics. Optionally, this is followed by a thermographic inspection to detect hidden defects such as micro-cracks and hotspots. Afterwards, you receive a report with photos and recommendations.

In a thermographic inspection, infrared cameras capture temperature differences that point to defects invisible to the naked eye, such as hotspots, faulty cells and string interruptions. The inspection is non-destructive and is carried out without dismantling the installation. On large solar parks, drones are used to scan extensive areas quickly.

A drone inspection combines high-resolution photography with thermal imaging and georeferencing to pinpoint and quantify defects precisely. This reveals hotspots, cold cells, faulty bypass diodes and string problems that an ordinary visual check would miss. The approach is particularly useful for large roofs, solar parks and hard-to-reach sites.

A hotspot is an area of a panel that overheats badly because a cell is no longer passing current, for example due to dirt, shading, a micro-crack or a cell defect. That cell then consumes energy instead of generating it, which reduces yield and, over time, creates a risk of fire or damage. A thermographic (drone) inspection detects hotspots early.

A visual inspection only reveals surface problems such as heavy soiling, broken glass, loose cabling or discolouration. Much of the yield loss and many safety risks, however, originate beneath the glass or in the connectors (micro-cracks, developing hotspots and PID degradation), and these can only be detected with thermography or electrical measurements. A combined approach gives you the full picture.

A visual and electrical check every two years is sufficient in many cases, while an annual inspection is advisable in environments with a lot of dust, salt or heavy industry. For larger installations and parks, a thermographic inspection every one to two years is recommended. An additional check is sensible after severe weather or if output drops for no apparent reason.

Maintenance includes a visual inspection for damage, loose cabling, broken clamps and hotspots, together with measurements and tests covering the inverter and yield data, among other things. The service also covers grounds maintenance, such as mowing between the panel rows. Regular maintenance extends the service life of your system, improves safety and helps keep your manufacturer's warranty valid.

Even a small amount of shade can noticeably reduce yield, so vegetation around and between the panels eats into your output. Overgrowth also gets in the way of maintenance access and can increase the risk of fire and damage. That's why Solarco keeps grass and weeds short, in an environmentally responsible way, with a report after every visit.

After 5 to 10 years, common problems include ageing cabling and connectors, loose clamps and rails, and micro-cracks, delamination and hotspots in the modules. Left untreated, these lead to structural yield loss, recurring inverter faults and a higher fire and safety risk. A combination of visual, thermographic and electrical checks catches them in time.

Soiling distorts thermographic and electrical measurements and can mask genuine defects, so the rule is: clean first, then measure, then decide. Clean panels are therefore a prerequisite for a reliable inspection. This way, you avoid drawing the wrong conclusions about the actual condition of the installation.

Yes. Solarco provides professional maintenance and cleaning for commercial roofs, farms, industrial installations and solar parks, using cleaning robots for large surfaces. We combine cleaning with thermographic inspection and vegetation management, and hold VCA safety certification, the Benelux safety standard for contractors. For recurring maintenance, we draw up a tailored contract.

Preventive maintenance is the inspection and thermography we use to assess the condition of your installation and detect problems early. Corrective maintenance only follows if defects come to light: we then carry out the necessary repairs. This means we only intervene where it's genuinely needed.

Most experts recommend a check at least every two years. In areas with a lot of dust, salt or heavy industry, or after extreme weather such as storms and hail, an annual inspection may be advisable. Together, we draw up a tailored plan based on the age, location and risks of your installation.

Using thermal imaging cameras, either drone-mounted or handheld, we map the temperature differences across your panels. This allows us to detect hotspots, faulty cells and soiling that you can't see with the naked eye, preventing yield loss and hazardous situations further down the line.

Yes. If the inspection or thermography reveals defects, we don't just hand you a report. We tackle the problems identified directly, from loose cabling to damaged components, so you don't have to go looking for another contractor.

After the preventive inspection, you receive a clear report setting out our findings and recommendations. It tells you exactly what steps are needed to keep your system running safely and at its best, and whether corrective maintenance is advisable.

Solarco cleans with professional equipment: suitable non-abrasive brushes and purified water, without harsh cleaning agents or high pressure. For large installations and solar parks, we use battery-powered, manufacturer-certified cleaning robots. A visual check and, if required, a thermographic check are carried out before and after cleaning.

No, washing-up liquid or soap is not recommended, because it leaves a thin film that attracts dirt and causes streaks every time it rains. That soap film absorbs light and so reduces output, while alkaline products can damage the coating over time. Clean with pure water and suitable brushes instead, without soap.

No, never use a pressure washer. The high pressure can cause micro-cracks, damage the seals around the panel and force water into the junction boxes, leading to faults and lost yield. Always clean at low pressure, with pure water and a soft, non-abrasive brush.

Safe cleaning calls for suitable non-abrasive brushes (with soft, flagged bristles that won't scratch) and pure water, without harsh cleaning agents or high pressure. A rubber squeegee used in one smooth downward stroke prevents streaks. For high or large roofs, professionals use telescopic poles or a cleaning robot, so nobody has to stand on the panels.

With manual cleaning, operators wash the panels by hand using pure water, soft brushes and fall protection; robotic cleaning uses autonomous machines that clean rows of panels with consistent pressure and water dosing. Manual cleaning is more flexible around obstacles and on complex roofs, while robotic cleaning is more efficient on large, continuous surfaces. Solarco chooses the method based on the type of installation.

No. Rain only washes away loose dust and often leaves minerals and stubborn dirt behind. Moss, lichen, bird droppings, pollen, Saharan sand and industrial fallout stay stuck to the panels, and it's precisely these layers that cost the most yield. Even a thin layer of dirt can mean 5 to 10% less output.

Since 2018, Solarco has specialised in the professional cleaning, maintenance and inspection of solar panels, serving more than 500 business clients in Belgium, the Netherlands, France and Germany. We work with purpose-built equipment and cleaning robots, carry out thermographic inspections and hold VCA safety certification. Our clients rate us 5/5 on Google Reviews.

VCA stands for 'Veiligheid, gezondheid en milieu Checklist Aannemers' (Safety, Health and Environment Checklist for Contractors), the Benelux safety certification for structured safety management on higher-risk work, such as working at height and with electricity. It is not a legal requirement in Belgium or the Netherlands, but professional clients often make it a contractual requirement. A VCA-certified partner such as Solarco gives you assurance on safety, procedures and liability.

No. Solarco cleans without leaving streaks and without damaging the panels, using suitable non-abrasive brushes and purified water, without harsh cleaning agents or high pressure. For large installations, we use manufacturer-certified robots. Our operators are certified, trained in fall protection and fully insured, so both your installation and your warranty remain protected.

We manage a wide range of sites: solar parks, road and motorway verges, municipal and public green spaces, business parks and sensitive nature areas. Whether it's a few hectares or an extensive site, we tailor our approach to the specific character of the location.

Vegetation that grows too tall around or under the panels casts shade, and even a little shade leads to a noticeable drop in yield. Good vegetation management also keeps the panels accessible for inspections, cleaning and repairs.

That depends on the location, the soil conditions and the type of vegetation. On some sites a single mow a year is enough; others need several visits per season. Plenty of rain and sunshine speeds up growth, which may call for additional maintenance visits.

Yes. We use environmentally responsible methods, such as electric or robotic mowers, and keep the use of chemical pesticides to an absolute minimum. That way, we keep the site tidy while preserving local biodiversity.

Certainly. On sites such as nature reserves, where peace and quiet and the ecosystem take priority, we deliberately choose low-noise, ground-friendly techniques that disturb the surroundings as little as possible.

After every visit, you receive a short report on the work carried out and the condition of the site. If there are specific challenges, such as invasive plant species or recurring weeds, we give tailored advice on tackling them for good.

You can easily request a quote through our website. We look at the specific characteristics of your site and propose a tailored approach and maintenance schedule, so you never pay for visits you don't need.