How to clean solar panels safely (and when not to)

How to clean solar panels safely (and when to avoid DIY)

If you are looking at getting solar panels for your home, you might also be wondering what kind of ongoing work they will require with regard to the cleaning, maintenance, and general care.

The good news is that it’s relatively easy to keep solar panels clean and in tiptop condition. You might also be pleased to learn that a little bit of rain can actually do them the world of good. The loose dirt and dust that can accumulate on them over time can often easily be washed away when it rains, meaning solar panels are generally low maintenance.

However, more stubborn grime like bird droppings, pollen, and other build-up can gradually build up, so understanding the right time to clean them properly and, more importantly, safely (and knowing when to avoid DIY jobs), can help protect your investment and ensure you get the most out of what they have to offer.

The underlying message we are trying to convey here and the golden rule that you must always remember is to NEVER CLIMB ONTO YOUR ROOF TO CLEAN SOLAR PANELS YOURSELF. Roofs can be slippery and are considered dangerous because working at height carries a serious risk of injury, no matter how experienced you are in this field.

If it’s not possible to easily reach your solar panels safely from the ground, the best course of action is to call in the professionals and don’t attempt to do it yourself.

Does rain clean solar panels in the UK?

The short answer is yes; frequent rainfall across the United Kingdom is relatively successful at keeping the majority of solar panels nice and clean, which helps them to be more productive and efficient. On roofs with suitable angles, rainfall is good at washing away loose dust and everyday surface dirt without you, the homeowner, having to put any extra work in.

However, rain isn’t the complete solution when it comes to keeping your solar panels clean. For instance, other stubborn deposits, such as bird-dropping stains, may stick to the glass long after a shower, just like on car windows or ones at home.

What does rain leave behind?

Some of the most likely culprits that can make your solar panels look dirty over time include the following:

– Bird droppings: This particular contaminant often ends up firmly sticking to glass and may partially cover one of your panels, which would decrease the amount of light that can reach the cells below.

– Tree sap: Dust, leaves, dirt, and various other deposits like this can get stuck to the tree sap, which can make the mess even more difficult to clean than with rain alone

– Pollen: Pollen has a tendency to leave a film across the surface of solar panels, particularly during the spring and summer seasons

– Leaves, moss and lichen: Natural debris and other organic growth often builds up around the edges of panels, or in some parts of systems where water/rainfall doesn’t easily drain away

– Traffic pollution: It’s also not uncommon for a gradual build-up of grime to occur on homes located near busy roads

If it is plain to see that your solar panels have dirt and grime either partially or fully covering them, rain might not be able to fully restore them to their original state of cleanliness, while at the same time, you don’t need to call in professional cleaners each time they get a little bit dusty.

The Energy Saving Trust solar panel cleaning and maintenance advice states that routine cleaning is not necessarily essential for many UK solar installations because rainfall removes much of the everyday dirt and light dust. Cleaning is only really worth considering when visible build-up is likely to affect the performance of your solar panels.

What happens if you don’t clean your solar panels?

Because daylight can be blocked by an accumulation of dirt and dust particles and other contaminant matter, it can cause your solar cells to be less productive. The exact impact on the output of your solar panels typically depends on the typical weather conditions, the amount and type of dirt they have on them, and how much of the panel is covered.  

• Efficiency drops

If your solar panel array is completely covered in muck and grime that rain hasn’t been able to wash away, the output from your system could dramatically suffer. Although it’s not a standard figure of reduction for every installation, some estimates put output loss due to dirty panels at between 5-20% of their normal capacity. Huge deposits can cause this figure to be higher, whereas insignificant light dust covering is unlikely to have much of an output effect at all.

• Hotspots

You don’t have to expect any permanent damage from the occasional sprinkling of light surface dirt and dust. It’s unlikely to interfere with the way the panel operates, but the same cannot be said of heavy or localised deposits, such as large bird droppings, which can have more of a negative impact on their output levels.

Furthermore, persistent localised shading and certain operating conditions can contribute to a hotspot, where a cell or area of the panel becomes unusually hot. It all depends on the panel design. Over time, hotspots can damage solar cells, but it doesn’t mean that every dirty patch you notice on your panels will cause one.

Helping protect how long solar panels last by keeping them reasonably clean as and when required is just one small part of maintaining your array. It is also equally important to keep a close eye on its performance and to investigate any faults that you notice rather than assuming that every drop in generation is because of the dirt that has accumulated on them.

• How to know when it’s time to clean

The quickest and easiest way to find out if your solar panel array needs cleaning is to monitor your system’s app, which enables you to identify any changes in output over time by comparing your findings from specific times throughout the year. 

When comparing performance over time via your system’s monitoring app, key things to look out for first include the following:

– Clear and obvious bird droppings, pollen and other build-up grime that rain is unable to remove

– Debris, such as moss and leaves, accumulating around the edges of your panels

– A noticeable drop in the output of your panels on a bright day compared with similar conditions previously

– A gradual reduction in output that can’t be explained by weather or the changes of the season

Don’t forget that it’s quite normal to get much lower output readings from your panels between October and March as the intensity of the sunlight is much less than in summer, and the days are shorter. Before you arrange for your solar panels to be cleaned, pay closer attention to whether the dip in output is consistent with the time of year and the type of weather you have recently experienced.

If the electricity generation from your solar panels has unexpectedly dropped, various factors could be the cause, such as a potential fault in the system, a build-up of dirt, or shading/shadows. If your array doesn’t appear to be dirty after a simple inspection, the best course of action would be to contact the company that installed them for you and see what advice they can offer you.

Can you clean solar panels yourself?

In certain situations and only under specific circumstances where it’s safe to do so, yes, it is possible to clean solar panels yourself. However, the Health and Safety Executive (HSE) warns that roof work is dangerous, even when the task seems quick or straightforward.

Falls from roofs and ladders can cause life-changing injuries or worse, death. HSE’s roof work safety guidance covers in much greater detail about avoiding work at height where reasonably practicable and using appropriate precautions when it cannot be avoided.

With this is mind, it means that most UK homeowners choose either a ground-based cleaning method or they will simply hire a professional with the correct access equipment and training required to clean your solar panels.

• The golden rule: never climb onto the roof

When you are attempting to reach the glass, NEVER stand on solar panels or climb onto the roof if it’s wet or covered in moss. Also, avoid walking across the roof tiles. Solar panels haven’t been designed to support a person’s weight, and roof surfaces can be slippery and dangerous even when they appear dry.

There are several other things you must also try to avoid. For example, never use a ladder while carrying, for example, a long brush or hose, and don’t lean out of upstairs windows. Losing your balance or reaching sideways out of a window may seem relatively simple, but it can potentially turn that simple cleaning task into a serious or deadly accident.

If it’s not possible to safely and comfortably clean the panels from stable ground, stop what you’re doing and arrange a professional cleaning job with the experts.

• System shutdown

Before attempting to give your panels a good clean, always check the instructions and remember to switch them off. Read the manufacturer’s instructions for your particular installation and carefully follow the specified shutdown procedure. Equally important is that you find out exactly which parts of the system can remain electrically live.

Always follow the instructions provided by your installer or manufacturer, especially if the procedure requires you to operate the inverter. Finally, make sure you never open electrical enclosures, handle damaged components, or disconnect any wiring.

It’s also worth noting here that just because you have switched the system off, it doesn’t necessarily mean that it’s now safe to touch. You must avoid things like damaged equipment, exposed wiring, and electrical connections coming into contact with water because solar panels can still produce DC electricity in daylight.

Also, avoid cleaning the panels if you happen to spot signs of water ingress, loose cables, or cracked glass. Get in touch with a qualified professional, and in the meantime, keep that area clear.

How to clean solar panels safely: tools and methods

If reaching the panels is safely possible from the ground, and the company that made the solar panels says that it’s ok to clean the panels in the manual, the best approach is usually a gentle one. You don’t need to be aggressive when cleaning them, and you won’t have to use any harmful or corrosive chemicals just to move run-of-the-mill dirt and build-up.

Step 1 (Timing): Choose a cool time of day

A sensible time to do the cleaning is in the morning or during a time of the day when it’s cool and overcast, so the panels aren’t hot from sitting in the blazing sun all day.

Water molecules tend to evaporate quickly when glass panels are hot, which could cause streak marks to be left behind. It’s also best to try and avoid sudden temperature changes during the cleaning process.

In other words, don’t pour freezing cold water onto heated glass solar panels. For best results, see what your solar panel manufacturer suggests on the most suitable cleaning methods and conditions.

Step 2 (Water): Use a gentle flow of water

Try to avoid using pressure washers because they can potentially damage your panels. All you need is a standard garden hose and a gentle flow of water instead of having it blasting out onto the panels that you can safely reach to rinse them off.

There are many areas in England where the water is classed as ‘hard,’ meaning that as this water dries on glass surfaces, it can leave mineral marks. To counter this, you might want to use suitably filtered or deionised water. Just make sure that it aligns with the manufacturer’s cleaning recommendations.

Always avoid spraying water on exposed connections, damaged cabling, and other electrical components.

Step 3 (Tools): Use a soft brush with a long handle

When dirt isn’t easily washing away, one of the most effective cleaning tools that can help bring your panels back to how they should look is a clean brush with soft bristles. To get to the harder-to-reach panels, you might want to attach the brush to a suitable telescopic extension pole.

Then, simply apply gentle brush strokes when cleaning and try not to put too much unnecessary stress or pressure on the glass panels or the mounting frame.  

To avoid putting yourself in a risky situation and potentially losing your balance and falling when you’re cleaning, and to prevent touching overhead power lines or damaging surrounding property, make sure you can manage the pole from standing on the ground.

As mentioned earlier, if you find yourself having to overstretch or strain just to reach the panels, stop what you’re doing immediately and arrange for the experts to come and do the job for you. Also, never stand on the panels or even use them as a foothold to help you reach other parts of the array.

Step 4 (Soap): Stick to plain water where possible

When it comes to routine cleaning, all that’s typically needed to get the job done quickly and effectively is a soft brush and a bit of clean water. Washing-up liquid and other cleaning products can leave residues that attract dirt or affect the surface.

Always remember to check the manufacturer’s guidance before using any detergent because things like washing up liquid and other products that you think might clean your panels well could end up leaving a nasty residue. Their guidance should be able to tell you which cleaning products are safe to use on the panels and which ones you must avoid using.

Never use a hard tool to scrape away tough stains and marks that don’t seem to be coming off easily. Instead, find out from the company who installed them what they think is the best course of action to remove those stubborn deposits.

Step 5 (Check): Check the result and monitor generation

After you have finished cleaning your solar panels, take another look at them while on the ground to ensure that the visible stains and dirt that you were trying to remove in the first place are no longer there. Don’t stand on the glass panels to inspect them.

Also, don’t forget that the app you can use to monitor your system can give you a much better picture as to whether or not your cleaning efforts have worked. They can show you whether the output of your panels improves in comparable weather conditions. After cleaning, don’t expect a huge difference in performance, especially if they were only lightly covered in dust before you started.

What you must never use on solar panels

Some popular cleaning methods can damage the panels. Although they may work well at home for you when cleaning certain things, they won’t work particularly well on solar panels. Bad cleaning materials and techniques can affect their seals or create unnecessary safety risks. Therefore, avoid the following things.

Don’t use pressure washers because they will likely damage seals. They also have a knack of forcing unwanted water into vulnerable areas, which has been known to harm wiring and other components. The solar panel surface can also be damaged by pressure washers.

Routine solar panel cleaning can usually be done with just a gentle hose spray and soft brush, especially when it’s just light dust and loose dirt. If there’s a lot of dirt and stubborn stains, don’t increase the water pressure or use tools and cleaning products that can potentially damage the equipment. Instead, arrange a professional clean.

Avoid using WD-40, harsh chemicals, solvents, abrasive cleaners or any other unapproved chemicals when cleaning the glass on your solar panels.

Products like this weren’t designed for routine solar panel cleaning, and they may cause residue or damage to surface coatings and seals. Instead, go by what the manufacturer’s recommendations are saying.

Similarly, avoid using things like wire brushes, abrasive tools, rough sponges, wire brushes, and scouring pads, wire brushes, rough sponges and abrasive tools because they can easily damage the surface coating or scratch the glass panels.

Scratches can turn out to be permanent and can significantly impact how much light reaches the cells. Also, use only soft cleaning tools approved for the panel surface.

Finally, avoid cleaning damaged panels or exposed wiring. If you spot a crack in the glass, find loose cables, or notice that electrical components appear damaged, don’t attempt to repair them yourself or apply water to these areas. Keep the area clear and get in touch with your installer or a qualified electrician with the relevant solar PV experience.

You should also apply this same rule to shutting down your system safely if you aren’t sure how to do it. Seek professional advice. It’s better to arrange help and guidance from the experts instead of putting yourself at risk of an electric shock, a fall, or damaging the installation.