Photovoltaic panel cleaning: how to do it and why it is important

How to maintain system efficiency over time with a few targeted interventions.

A photovoltaic system is designed to produce energy for decades, but its yield also depends on how much care is dedicated to it over time.

Module cleaning is one of the fundamental ordinary maintenance interventions: if carried out regularly, it allows you to recover a share of production that dirt would tend to progressively reduce.

What happens if photovoltaic panels are not cleaned?

Solar panels work outdoors, exposed every day to dust, smog, pollen and organic residues. As the seasons pass, these deposits form an opaque layer that obstructs the passage of light towards the photovoltaic cells, progressively reducing the energy efficiency of the panels.

The extent of the drop in photovoltaic production linked to dirt varies significantly based on the context: the geographical area, proximity to busy roads, agricultural or industrial areas, and the frequency of rainfall are all factors that affect the rate of deposit accumulation. In typical Italian conditions, losses are limited, but in particularly critical environments, such as coastal areas with high salinity, areas with a strong presence of particulate matter or contexts with a long dry season, the impact on performance can become significant.

A frequent case in Italy, especially in the Central-Southern regions, is the deposit of Saharan dust: the fine particles that settle after episodes of wind from the South form a compact layer that is difficult to remove with rain alone and require timely manual intervention.

The problem is that this drop is gradual and difficult to perceive without monitoring production data. Nothing breaks, but performance decreases steadily over time, silently eroding the value of the investment.

A separate case is bird droppings on solar panels: unlike dust, which is distributed evenly, droppings create localised shading that can penalise the production of the entire string of the system. They must be removed promptly, without waiting for the ordinary cleaning cycle.

When to clean the panels and why it is convenient to do it

Ordinary cleaning of the photovoltaic system does not require frequent interventions. The ideal frequency is 1–2 times a year, with one cleaning in spring to remove winter deposits (smog, pollen) and one in autumn to prepare the system for the months with lower irradiation. Those who live in coastal, agricultural or industrial areas should plan closer interventions.

One factor that directly affects the frequency of interventions is the angle of inclination of the modules. Panels installed with an inclination greater than 15° benefit from a natural self-cleaning effect: rainwater flows over the surface, removing much of the dust. Below 10°, instead, deposits tend to accumulate more quickly and require more frequent manual interventions, an element to consider already during the system design phase.

Regular cleaning allows you to recover the share of photovoltaic panel performance lost due to accumulated dirt, with a direct impact on self-produced energy and, consequently, on savings in your bill. The cost of the intervention, whether do-it-yourself or entrusted to a professional, is generally lower than the value of the energy recovered over the year.

How often to clean photovoltaic panels

Dirt factor	Recommended frequency	Operational note
Frequent rainfall (🟢 low priority)	Once a year	The self-cleaning action of rain reduces deposits. One intervention in spring is generally sufficient.
Pollen and organic dust (🟢 low priority)	1–2 times a year	Spring deposits compact quickly. Intervene at the end of spring and, if necessary, in autumn.
Saltiness and coastal humidity (🟡 medium priority)	2 times a year	Sea salt forms residues that are difficult to remove with rain alone. Cleaning is recommended in spring and late summer.
Saharan dust (🟡 medium priority)	Timely intervention	Deposits form unpredictably and must be removed immediately, without waiting for the ordinary cycle.
Smog and industrial particulate matter (🔴 high priority)	2–3 times a year	Chemical residues reduce performance quickly. Monitor production data regularly.
Bird droppings (🔴 high priority)	Immediate removal	They create localised shading that penalises the entire string. Do not wait for the ordinary cleaning cycle.

Do-it-yourself or professional: how to choose

The choice mainly depends on three factors:

system size
roof accessibility
type of intervention required

For small systems on flat or easily accessible roofs, do-it-yourself is a practical and economical solution. For sloping roofs, surfaces that are difficult to reach or medium and large-sized systems, relying on a specialised technician is the safest choice.

Professionals do not limit themselves only to the physical cleaning of the modules: they also carry out wiring inspection, verification of electrical connections and control of the general condition of the panels. This is a complete maintenance intervention on the system, which allows any anomalies to be identified before they turn into faults.

Regarding the cost of cleaning photovoltaic panels, there is no fixed figure: it depends on the size of the system, roof accessibility, geographical area and the type of service included. To have an accurate quote, the advice is always to contact a qualified technician who can assess the specific case.

How to clean photovoltaic panels do-it-yourself

For small systems installed on flat and easily accessible surfaces, do-it-yourself cleaning is a feasible option: only a few tools and some precautions are needed to operate correctly without risking damage to the modules.

Demineralised water is the fundamental element of the photovoltaic panel cleaning kit. Tap water contains limescale which, once evaporated, leaves white residues on the glass surface, further reducing the transparency of the panel.

Use microfibre cloths or soft-bristle brushes. Avoid rough materials that can scratch the surface.

In the presence of stubborn deposits, such as limescale encrustations or residues of compacted Saharan dust, use only products formulated for photovoltaic systems, free of aggressive chemical agents and compatible with anti-reflective coatings.

Do not use aggressive chemical detergents, solvents and non-adjustable high-pressure washers. These products can damage the glass, deteriorate the perimeter sealants of the module and, over time, compromise the watertightness of the entire panel.

Prefer the early morning hours or late afternoon, when the panels are not overheated by direct sun. Cleaning a hot panel with cold water can cause micro-cracks in the glass due to thermal shock.

Protect the value of your system with Enel and 3SUN

Photovoltaic panel cleaning is one of those interventions that require little effort but deliver concrete results: more energy produced, more savings in your bill and longer system life. With the right frequency and suitable tools, it simply becomes part of the routine of those who have chosen to invest in solar energy.

Among the available solutions, the Solare Italiano by 3SUN range offers modules produced in the Catania Gigafactory, the largest in Europe dedicated to photovoltaic.

If you are evaluating a new system or want to replace existing modules with certified solutions, discover more about Solare Italiano by 3SUN and evaluate the solution best suited to your needs.

Self-produce energy and save up to 60% on your bill

Photovoltaic system with design, installation and ENEA procedure management included starting from €3,500. In addition, if you are an Enel power customer or become one, you get a €360 bonus in your bill.

Learn more

Frequently asked questions about photovoltaic panel cleaning

Partially. Rain removes much of the surface dust, but it is not able to eliminate bird droppings, compacted pollen deposits or limescale encrustations. Panels with a good inclination benefit more from the self-cleaning effect; those installed almost flat instead tend to accumulate more residues and require more frequent manual interventions.

No. Household detergents often contain ammonia or alcohol that can damage the anti-reflective coatings of the panels and deteriorate the perimeter sealants of the module. For do-it-yourself cleaning, demineralised water is sufficient, as it leaves no residues and is compatible with all panel materials.

Yes. Inclination favours the flow of rainwater and reduces the accumulation of dust and debris. Modules installed at a good angle benefit from a natural self-cleaning effect, while those mounted almost horizontally retain more dirt and require more frequent interventions. It is a factor to consider already during the system design phase.

The most reliable signal is a persistent drop in production data, not explained by weather conditions or the season. Most modern systems are equipped with monitoring systems accessible via app: comparing current production with that of the same period of the previous year allows anomalies to be identified quickly. A gradual and constant drop, in the absence of new shading or faults, is often attributable to accumulated dirt.

It depends on the power of the system. For systems with power greater than 11.08 kW, periodic cleaning is mandatory by law, with technical checks to be carried out every five years by qualified personnel. For residential systems with lower power, there is no specific cleaning obligation, but DM 37/2008 requires the owner to maintain the system in safe conditions, which includes adequate ordinary maintenance.

Yes, in both cases a check is advisable. After an intense hailstorm, it is useful to visually check the surface of the panels to detect any microfractures in the glass, which can compromise performance over time. After a sandstorm or an episode of Saharan dust, the deposits that form are often too compact to be removed by subsequent rain and require manual intervention. These are extraordinary situations that are added to the ordinary cleaning cycles, without replacing them.