Do you need to clean solar panels? Find out how often and how to

We all want to keep kerb appeal up and having clean solar panels is one of the many maintenance tasks a modern homeowner must consider. 

The majority of solar panels in the UK are actually self-cleaning, which means that they have a hydrophobic coating that protects the panel surface by preventing water droplets from sticking to them. This prevents the gradual build-up of minerals on the solar cells, because when droplets of rain fall from the sky they bring particles of dirt with them. 

However, this often isn’t enough to keep the panels clean and generating electricity as efficiently as possible means that the panels also have to be cleaned periodically. This guide explores how you should do that.

Do solar panels need to be kept clean? 

Solar panels need to be kept clean in order to prevent dirt and grime from building up on the surface of the panels and reducing their efficiency. Cleaning after solar panels will help to keep them at maximum efficiency, therefore helping to lower your overall household energy bill.

Plus, given the upfront cost of solar panels, keeping this renewable technology is good shape with careful maintenance should be at the forefront of a homeowner's mind.  

This is especially true if you benefit from solar panel grants whereby the efficiency of your solar array could impact the amount the grid will pay you for surplus solar energy.

How often should solar panels be cleaned? 

How often you clean your solar panels may depend on the type of panels you have installed and the advice of the company that installed them initially and/or the manufacturer.

Typically you'll need to clean your panels every six months, or at least one a year. (You may need to clean them more frequently if they are exposed to dirt and grime, for instance, in an urban area or in close proximity to trees.)

That said, most solar pv panels in the UK will not need any heavy-duty cleaning because regular rain will wash most dirt and grime off the surface.

Is it advisable to pay a professional to clean solar panels?

If time is short, you may decide to pay a professional to clean your solar panels instead. It is also safer if you feel someone needs to get up on the roof to clean them and you do not have the right equipment or are not confident working at height.

In the UK, paying a professional to clean the panels will cost somewhere between £40 and £300 (according to Checkatrade), reflecting the cost of safety equipment and training, ease of access and the condition of the panels.

Also, if you have a solar powered house, or has a vast solar array, paying a professional may be well worth the money compared with the time and effort of DIY. 

Can I clean my own solar panels? 

You can clean your own solar panels, but doing so may affect the warranty, which is a good reason to hire a professional instead. Special solar panel cleaning kits are available consisting of biodegradable soap, a wiping implement and a brush (like this 3-in-1 design from Amazon). 

Simply mix the soap with water in a bucket and then apply with the brush, wiping afterwards with the wiper. It’s really important that you use a soft brush, as any abrasive tool will scratch the glass on the panel. It’s safer to use a long-handled brush that can be used from the ground. 

Use a safety harness and ropes if you feel you need to climb up onto the roof, especially given the roof is likely to be slippery. 

If you are short on time, cleaning the panels regularly with a hose pipe might be enough to get rid of any small amounts of dirt or grime before they build up. Another option is to install an automatic cleaning system as part of your solar panel array. These systems are equipped with sprinklers. 

How to clean solar panels

A monthly wash with a hose pipe may be enough for a while to get rid of the dirt and grime that is not otherwise washed away by the rain. However, this may not get rid of any accumulated moss that may have built up.

In hot weather, bear in mind that using a hose pipe to spray cold water on the panels may potentially damage them, so on these occasions it is best to do this in the early morning or in the evening.

This happens when the glass is hot and so pouring cold water on it causes it to experience a sudden extreme temperature change (thermal stress), rendering it brittle. Over time, with repeated treatment in this manner, the glass could potentially crack. Even if this does not happen, cleaning the panels on a hot day will also leave smudges on the glass because the sun will evaporate the water too quickly. 

Special kits are available for cleaning solar panels, usually consisting of biodegradable soap, a wiping implement and a soft brush, sometimes with a long handle. A soft rag can also be used for cleaning the panels.

Avoid using any abrasive implements or harsh chemicals or you may damage the panels.

Is it OK to power wash panels? 

Solar panels are not designed to take the impact of a high pressure stream of water from a pressure washer.

Furthermore, a grid-connected solar panel array with solar batteries is a high voltage electrical system which is potentially dangerous if it is damaged. Doing this will therefore almost certainly invalidate the warranty.

Can you use vinegar to clean solar panels? 

Vinegar is a great cleaning agent for solar panels because it contains acetic acid, which is very capable of breaking down tough stains, dirt and grease. It is also readily available and any vinegar will do although the best type to use is white cleaning vinegar. 

The way to use it is to make a dilute solution using a quarter cup of vinegar and two cups of water plus half a teaspoon of liquid detergent or non-abrasive soap. To apply it, pour it into a spray bottle.

How do you clean moss off solar panels? 

Lichen growth on solar panels is driven by microscopic algae living alongside it in a symbiotic relationship. Lichens are not plants and they produce their own food via photosynthesis, eliminating the need for water.

This means they can grow in locations where other plants would not survive — solar panels being one such location. The only way to remove lichen from solar panels is to remove the algae that stimulates its growth.

This is another reason for cleaning solar panels regularly. Some companies use special anti-algal chemicals to remove lichen once it starts to become established. However, a diluted vinegar solution is also effective which will also kill moss, which tends to grow especially in locations where there is a high atmospheric moisture content.

How do you clean bird droppings from solar panels? 

Birds often see solar panel arrays as an attractive place to perch and nest and droppings can also be a problem. To deter birds, the solar panels should be kept free of debris such as twigs and other detritus. A thin strand of chicken wire attached to the edge of the panels preventing any access to the underside of the panels is also a good idea. 

To clean droppings off the surface, regular cleaning with a mild detergent should be sufficient, a soft brush on a pole is even better to help scrub the droppings off, as they tend to be more resilient than other dirt and grime.

How do you clean solar panels without water? 

Most professionals do not recommend the use of chemicals to clean solar panels without using water. However, earlier this year, a team of scientists at Massachusetts Institute of Technology (MIT) devised a new water-less approach using electrostatic repulsion to push dust particles off the surface of the panels. 

In this approach, an electrode passes over the panel surface and the electrical charge it produces repels the dust particles. Initially, this would be more suitable for commercial and industrial-scale solar farms, as it uses an electric motor that runs on rails along the edge of the panels, but if successful a version of it might become available for domestic use.

Other researchers at the University of Washington have developed an alternative approach which uses a self-cleaning surface based on mechanical vibration.