Solar panels are designed to spend years exposed to rain, wind, dust and changing weather, but that does not mean they should be cleaned with whatever household product is sitting under the kitchen sink. One of the most common questions homeowners ask is whether washing-up liquid can be used to clean solar panels.
The simple answer is that it is generally better to avoid washing-up liquid. While it may seem gentle enough for glass, household detergents can leave a film behind and may contain ingredients that are not intended for photovoltaic panel surfaces. Solar Cleaning South West uses purified water and soft-bristle brushes to clean panels without relying on harsh chemicals.
Why Washing-Up Liquid Seems Like a Good Idea
It is easy to see why washing-up liquid gets recommended for DIY solar panel cleaning. It is readily available, designed to remove grease and grime, and is mild enough for many household cleaning jobs.
Solar panels, however, are slightly different from ordinary household glass.
The surface of a photovoltaic panel needs to allow as much sunlight as possible to reach the cells beneath the glass. Some modern panels also have surface coatings designed to improve performance and reduce reflection. A cleaning product that leaves behind residue is therefore not necessarily helpful.
The Energy Saving Trust advises avoiding washing-up liquid because it can leave a film on the panels if it is not rinsed away properly, potentially making it easier for dust to accumulate.
What Happens If You Use Washing-Up Liquid?
The biggest issue is usually residue rather than the initial cleaning process.
After applying detergent, it can be difficult to rinse every trace away, particularly when cleaning panels on a roof. Any remaining film can create streaks or attract further dirt.
This means you could clean your panels only to find that they become visibly dirty again sooner than expected.
There is also the question of the specific ingredients in the detergent. Washing-up liquids vary considerably between products, so it is not sensible to assume that every formulation is suitable for photovoltaic glass.
For this reason, specialist solar panel cleaning generally takes a simpler approach.
| Cleaning method | Suitability for solar panels |
|---|---|
| Purified or deionised water | Excellent |
| Soft, non-abrasive brush | Excellent |
| Washing-up liquid | Generally best avoided |
| Abrasive cleaners | Avoid |
| Strong chemicals | Avoid |
| Pressure washing | Avoid |
| Household scourers | Avoid |
What Is the Best Way to Clean Solar Panels?
For routine solar panel cleaning, purified water and an appropriate soft brush are often all that is required.
Solar Cleaning South West uses purified water and soft-bristle brushes to remove dirt, dust, bird droppings and other contamination while providing a streak-free finish. The company provides solar panel cleaning throughout Bath, Bristol and the wider South West, covering both domestic and commercial installations.
Purified water is particularly useful because it contains fewer minerals than ordinary tap water. When tap water dries on glass, it can leave behind mineral deposits and spotting. These marks can make freshly cleaned panels look dirty and may require additional cleaning.
A gentle cleaning method also avoids putting unnecessary stress on the glass, seals and surrounding components.
What About Stubborn Bird Droppings?
Bird droppings can be considerably harder to remove than loose dust or pollen.
Rather than scrubbing aggressively with a household cleaner, the contamination should be softened and removed using an appropriate method. Scrubbing too hard or using an abrasive material can create scratches.
Specialist solar cleaning products are available for situations where purified water alone is not sufficient. Solar Cleaning South West highlights the use of eco-friendly cleaning techniques and specialist products where more stubborn contamination requires additional treatment.
The key is to remove the contamination without damaging the surface in the process.
Can You Clean Solar Panels With Just Water?
For many solar panel installations, yes.
In fact, plain purified water is often preferable to adding household detergent. It can remove everyday dust, pollen and loose dirt without leaving a soapy residue.
This is one reason professional solar panel cleaning can look different from cleaning ordinary windows. The objective is not simply to make the glass look clean. The process needs to leave the surface clear while avoiding unnecessary chemicals and abrasive equipment.
If your panels have significant bird fouling, organic matter or another stubborn substance, the appropriate cleaning approach will depend on the contamination and the panel manufacturer’s guidance.
Should You Use Tap Water?
Tap water can be used for some cleaning situations, but it is not always ideal.
Water contains dissolved minerals, and these can remain on the glass after evaporation. The result can be water spots, streaks and deposits that are particularly noticeable on dark solar panels.
Purified or deionised water avoids much of this problem because there are fewer minerals available to remain on the surface.
For a professional solar panel cleaning service, this can make a significant difference to the finished appearance.
Never Use a Pressure Washer on Solar Panels
If you are considering DIY cleaning, washing-up liquid is not the only thing to think about.
Pressure washing should also be avoided. High-pressure water is unnecessary for routine solar panel cleaning and can potentially cause damage to seals and other components. Solar Cleaning South West specifically advises against pressure washing and recommends gentle cleaning methods instead.
Abrasive brushes, scourers and harsh chemicals should also be avoided.
The aim is to remove contamination, not aggressively scrub the panel surface.
Is DIY Solar Panel Cleaning Safe?
There is another consideration that has nothing to do with the cleaning product: working at height.
Many solar panels are installed on pitched roofs, conservatory roofs, garages or other difficult-to-access areas. Trying to reach them with a bucket and brush can create a significant fall risk.
You should never stand or walk on solar panels. Apart from the obvious safety issue, putting concentrated weight onto the panels can potentially damage them.
If your solar panels are difficult to reach safely from ground level, professional solar panel cleaning is a much more sensible option.
How Often Should Solar Panels Be Cleaned?
There is no single cleaning schedule that suits every property.
A home surrounded by trees may experience more pollen, leaves and bird activity than a property in an open area. Coastal locations can also experience different types of airborne contamination.
Solar Cleaning South West recommends cleaning solar panels at least once or twice a year, with more frequent cleaning potentially being appropriate where panels experience heavier levels of dust, pollution or bird activity.
Regular cleaning can help keep the surface clear and ensure your solar investment continues to perform effectively.
Professional Solar Panel Cleaning in the South West
So, can you use washing-up liquid to clean solar panels? Although some panel manufacturers may permit specific mild detergents under controlled circumstances, it is generally better not to use ordinary household washing-up liquid unless the manufacturer’s instructions specifically recommend it.
For routine cleaning, purified water and soft, non-abrasive equipment provide a straightforward approach without leaving a soapy film behind.
For homeowners in Bath, Bristol and across the South West, Solar Cleaning South West provides professional solar panel cleaning using purified water and soft-bristle brushes. This provides a thorough clean while avoiding harsh chemicals and high-pressure methods.
Clean panels are not simply about appearance. Keeping the glass free from dirt, bird droppings and other deposits helps maintain the surface through which your solar system receives sunlight.
Why Clean Solar Panels at All?
Solar panels are designed to work outdoors, so a certain amount of dirt and weather exposure is unavoidable. Rain will naturally wash away some surface dust, but it does not remove everything that can build up over time.
Pollen, dust, traffic pollution, bird droppings, leaves and other organic debris can gradually accumulate on the glass. In areas with lots of trees, the problem can be more noticeable, particularly during spring and autumn.
The effect of dirt will depend on how much contamination is present and where it sits on the panel. A light layer of dust may have relatively little impact, while heavy deposits or bird fouling can create more significant areas of obstruction.
Cleaning is therefore less about making solar panels look attractive and more about keeping the surface clear.
Does Rain Clean Solar Panels Properly?
Rain certainly helps. It can remove loose dust and some of the lighter contamination from the surface.
However, rain should not be considered a complete replacement for professional cleaning.
Rainwater can leave behind deposits as it evaporates, particularly when it carries airborne dirt or contaminants onto the glass. Bird droppings can also remain stuck to the surface despite repeated rainfall.
The shape and angle of your roof can make a difference too. Some panels will naturally shed water and dirt more effectively than others.
If you have noticed visible marks, stubborn deposits or patches of contamination that remain after several periods of rainfall, it may be time to consider a proper solar panel clean.
Why Bird Droppings Can Be a Particular Problem
Bird droppings are one of the more noticeable forms of solar panel contamination because they can create concentrated areas of dirt rather than an even coating across the entire panel.
A single deposit may cover a relatively small area, but the problem can become more significant if birds regularly use the roof, chimney or nearby trees.
Trying to remove dried bird droppings by aggressively scrubbing the panel is not recommended. Hard particles within the dried material can potentially act as an abrasive if they are rubbed across the glass.
A gentler approach is preferable. The contamination can be loosened and removed using suitable equipment without resorting to excessive pressure or household scourers.
This is another reason professional solar panel cleaning can be preferable to simply climbing onto the roof with a bucket and sponge.
Why Soft Brushes Are Used
A solar panel cleaning brush needs to be capable of removing contamination without unnecessarily scratching or damaging the glass.
Soft-bristle equipment provides a way of agitating dirt while keeping the cleaning process relatively gentle.
The brush also needs to be used correctly. Applying excessive force is rarely necessary for normal surface contamination. The objective is to allow the water and brush to loosen the dirt rather than trying to grind it away.
This approach is particularly useful when cleaning larger domestic or commercial solar installations where there may be dozens of panels to work across.
Why Purified Water Makes a Difference
One of the biggest differences between professional solar panel cleaning and a typical DIY approach is the water used.
Ordinary tap water contains minerals. Once the water evaporates, those minerals can remain behind as small deposits on the glass.
You may have seen the same effect on windows, shower screens or cars. A surface can be completely wet and appear clean, but once the water dries, white spots and streaks become visible.
Purified water contains far fewer of these dissolved minerals, helping it dry more cleanly.
This is particularly useful when cleaning solar panels because there is little benefit in removing one type of contamination only to leave another visible residue behind.
Could Washing-Up Liquid Damage Solar Panels?
It is worth making a distinction between damaging the panels and being an unsuitable cleaning choice.
Using a small amount of washing-up liquid is unlikely to automatically destroy a solar panel. The bigger concern is that ordinary household detergent is not specifically formulated for photovoltaic panel cleaning.
Different products contain different combinations of surfactants, fragrances, additives and other ingredients. Some can leave a residue, particularly if the surface is not rinsed thoroughly.
There is also little reason to introduce detergent when purified water and appropriate cleaning equipment can often deal with everyday contamination effectively.
The safest approach is always to follow the solar panel manufacturer’s cleaning and maintenance instructions.
What Should You Avoid When Cleaning Solar Panels?
A simple rule is to avoid anything unnecessarily aggressive.
This includes abrasive pads, scourers, stiff brushes and harsh cleaning chemicals. High-pressure equipment is also unsuitable for routine solar panel cleaning.
You should also avoid walking across the panels. Solar panels may look robust, but they are not designed to be used as a walkway.
Another common mistake is attempting to clean panels during very hot, sunny conditions. Water can evaporate rapidly from a hot surface, making it more difficult to achieve an even finish and potentially leaving deposits behind.
A cooler part of the day can be more practical for cleaning.
Does Cleaning Improve Solar Panel Performance?
The purpose of cleaning is to remove material that is obstructing the panel surface.
How much difference this makes depends heavily on the condition of the panels beforehand. A lightly dusty installation will not necessarily experience the same change as one covered in heavy bird fouling, pollen or accumulated dirt.
It is therefore difficult to give one universal percentage improvement that applies to every solar installation.
What can be said is that clean glass allows sunlight to reach the photovoltaic cells without a layer of dirt sitting between the light and the panel.
For homeowners who have invested in solar technology, keeping the installation properly maintained makes practical sense.
Should New Solar Panels Be Cleaned?
New panels are usually relatively clean when installed, so immediate cleaning is not normally necessary simply because they are new.
Over time, however, they will begin to accumulate normal outdoor contamination.
The right cleaning frequency depends on the property’s surroundings. A rural property surrounded by trees may experience different conditions from a home close to busy roads or commercial areas.
Bird activity is another factor.
Instead of automatically booking cleaning every few months, it is often more useful to inspect the panels periodically and consider the environment around them.
What About Solar Panels on Commercial Buildings?
Solar panel cleaning is not limited to domestic properties.
Commercial buildings, offices, warehouses, agricultural buildings and other premises can have much larger installations. With more panels exposed to the elements, there is potentially a greater surface area for dirt and contamination to accumulate.
Commercial systems can also be more difficult to access safely, making professional cleaning particularly useful.
A planned maintenance schedule can help businesses keep the installation clean without relying on occasional DIY cleaning.
Can Window Cleaners Clean Solar Panels?
There are similarities between window cleaning and solar panel cleaning, but the two services are not exactly the same.
Solar panels require suitable equipment and an understanding of the surface being cleaned. The access arrangements can also be completely different, particularly when panels are installed on pitched roofs.
A company that specialises in solar panel cleaning will have equipment designed to work across the panels while minimising unnecessary pressure and contamination.
Solar Cleaning South West provides specialist solar panel cleaning across the South West, using methods designed specifically for photovoltaic panels rather than treating them simply as ordinary windows.
How Can You Tell When Solar Panels Need Cleaning?
There are several obvious signs.
Look for visible dust, bird droppings, dark patches, streaking, moss or other organic contamination. If the panels are positioned beneath trees, check for leaves and pollen deposits.
You may also notice that some panels look noticeably dirtier than others. This can happen where sections of an installation are exposed to different conditions.
If you cannot safely inspect the panels from ground level, do not attempt to climb onto the roof simply to check them.
A professional cleaner can assess the condition and determine whether cleaning is actually required.
Is Solar Panel Cleaning Worth Paying For?
For homeowners with safely accessible panels, occasional DIY cleaning may seem straightforward. However, the situation changes when panels are installed on a roof or another difficult-to-reach location.
Professional cleaning removes the need to work at height and provides access to appropriate equipment and cleaning methods.
It also avoids the common DIY mistake of treating solar panels like ordinary household windows and reaching for washing-up liquid, abrasive sponges or pressure washers.
For many homeowners, the main benefit is therefore convenience as much as cleaning itself.
Final Thoughts on Washing-Up Liquid and Solar Panels
Washing-up liquid might be perfectly suitable for plates, glasses and many household surfaces, but solar panels require a more considered approach.
Rather than relying on household detergent, purified water and soft, suitable cleaning equipment provide a straightforward way to remove everyday contamination without leaving behind a layer of soapy residue.
For panels affected by stubborn dirt, bird droppings or significant build-up, professional cleaning can provide a safer and more thorough solution.
Solar Cleaning South West offers specialist solar panel cleaning throughout the South West, using purified water and soft-bristle brushes rather than aggressive cleaning methods. Keeping panels free from unnecessary contamination helps maintain a clean surface and protects the investment you have already made in your solar installation.