Solar panel cleaningWith nobody on the roof
We clean solar panels with purified water and technology controlled from the ground, such as drones, choosing the most efficient approach for each roof. It makes most sense on flat or low-pitch commercial roofs, and for panels near farmland, a railway or an industrial estate, where dirt builds up quickly. Every clean is planned, tracked and reported on the OPPY platform, our client portal.
On a pitched roof in open surroundings, rain does much of the work. We'll tell you that too, before you book a clean.
How a clean works
- 01
Intro call
In a 30-minute call you tell us about your installation: number of panels, roof type, surroundings and anything you have noticed in the production figures.
- 02
Remote assessment or site visit
We look at the roof, access and how dirty the panels are, to decide whether cleaning is worthwhile and how often.
- 03
Authorisation and scheduling
Cleaning with a drone falls under the specific category of the EU drone rules, which requires an operational authorisation, issued in Belgium by the Directorate-General Aviation of the FPS Mobility and Transport (Federal Public Service). We schedule the flight around the weather and around how your site operates.
- 04
Cleaning
We mark out a safety perimeter on the ground. The pilot flies the drone over the panels row by row, and nobody has to go up on the roof.
- 05
Report on the platform
After the clean, the report with before and after photos is on the platform, along with anything else we noticed on the roof.
Purified water, low pressure and nobody on the roof
We clean with purified water: mains water with the minerals removed by reverse osmosis. With nothing left in it, the water dries without streaks or limescale spots and leaves no film on the glass to hold back the light.
We loosen dirt with low pressure and soft brushes, never with a pressure washer, which can damage the anti-reflective layer or the panel seals. The drone flies above the array, so nobody walks on the roof or leans on a panel.
After cleaning, we can apply a dirt-repellent coating. Dirt sticks to it less and rain carries more of it away, so the panels stay cleaner for longer. They still need cleaning, though often less frequently.
Where cleaning makes a real difference
Soiling costs yield, but less than you often read. A European study by DLR (Renewable Energy, 2024) puts the average annual loss at 0.9% if rain is counted as perfect cleaning, and up to 5.3% if rain cleans only 10%. Measurements in Belgium found roughly 3 to 4% power loss from dust. So we don't promise big yield gains. On these roofs, though, cleaning matters:
Flat and low-pitch commercial roofs
Rainwater sits and evaporates, and dirt collects along the lower edge of each panel. Across a large roof, a small loss per panel adds up.
Panels near farmland, railways or industry
Field dust, brake dust from trains and fallout from nearby production stick to the glass. Rain alone won't shift them.
Bird droppings
They leave a hard, opaque patch over part of the cells, and rain barely touches them.
Pitched roofs in open surroundings
Here rain does most of the work. Yearly cleaning is often unnecessary, and we won't recommend it if it doesn't pay.
Drone, by hand, aerial work platform or robot
There are several ways to clean solar panels. These are the differences that matter most to a facility manager.
Solar panel cleaning methods compared
| Drone (OPPY) | By hand, on the roof | From an aerial work platform | Cleaning robot | |
|---|---|---|---|---|
| Work at height | No, the pilot stays on the ground | Yes, with fall protection and roof access | Yes, in the platform basket | Someone has to place the robot on the panels and take it off again |
| Site preparation | A marked-out safety perimeter on the ground | Roof hatch or ladder, edge protection or harnesses | Clear, firm ground next to the building | Continuous rows of panels the robot can drive along |
| Contact with the panels | Low pressure and soft brushes, nobody on the panels | Brush and squeegee, risk of someone leaning on a panel | Brush or lance at a distance, reach limited by the boom | Rotating brush that runs over the glass |
| Reporting | Report with photos and findings on the platform | Depends on the contractor | Depends on the contractor | Depends on the contractor |
How much does solar panel cleaning cost?
We price per panel or per kWp (kilowatt peak). What sets the price:
- the number of panels or the size of the system
- the roof type and pitch
- access, and space for a safety perimeter on the ground
- how dirty the panels are, and with what
- how often we come: a one-off clean or a regular programme
The result, roof by roof, on the platform
After every clean, the report goes onto the OPPY platform, our client portal: before and after photos, and anything we spotted, such as a cracked panel, a loose cable or a nest under the array, with its location on the roof. For each building you can see when it was cleaned and what was found.
If you manage several sites, it is all in one place. You can export the report as PDF or CSV for your maintenance plan or ESG reporting.
Solar panel cleaning: common questions
How often should solar panels be cleaned?
There is no fixed rule. On a pitched roof in open surroundings, rain washes off much of the dirt, and cleaning every few years may be enough, or none at all. On a flat or low-pitch roof, or next to farmland, a railway or a factory, dirt builds up faster. There we agree a regular interval with you, based on what we see on the roof and on your production figures.
Is it worth cleaning solar panels?
It depends on your roof and its surroundings. A European study by DLR (Renewable Energy, 2024) puts the average annual soiling loss at 0.9% if rain is counted as perfect cleaning, and up to 5.3% if rain cleans only 10%. On a large array on a flat commercial roof, that difference can be worth more than the cleaning costs. On a small pitched roof it often won't, and we'll tell you so.
Does an anti-soiling coating affect my panel warranty?
We check this for your panels before applying any coating. If there is any doubt, we clean without a coating: purified water at low pressure leaves no residue on the glass. Send us the make and model of your panels and we'll check before the job.
Isn't rain enough to keep solar panels clean?
On a pitched roof it often is, for loose dust. Bird droppings, baked-on dust and moss or lichen growth usually stay put. On a flat or low-pitch roof, rainwater sits on the panel and evaporates, leaving the dirt in a band along the lower edge. That is where rain helps least and cleaning pays off most.
How much does solar panel cleaning cost per panel?
The price depends on the number of panels or the system size in kWp, the roof type and pitch, access, how dirty the panels are and how often we come. In a 30-minute call we can give you a price for your installation.
Not sure cleaning will pay off?
In 30 minutes we go through your installation, its surroundings and your production figures. You'll come away knowing whether cleaning makes sense, and roughly what it would cost.