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Should I clean my solar PV panels?

Posted by Sam Tonge on 12 September 2018 at 10:15 am


POLL CLOSED: Here are readers' responses to whether they clean their PV array. (The survey of 62 respondents was carried out between 12th September and 15th October 2018). 

Following the recent spell of dry weather in much of the UK, we’ve had a number of enquiries about whether it’s necessary to clean your solar PV panels to make sure they remain as efficient as possible.

A quick Google search for ‘solar panel cleaning’ pulls up a long list of adverts for specialist cleaning firms. However there is an ongoing debate between owners of solar installations in the UK as to whether the periodic cleaning of panels is actually necessary or even beneficial to increase output.

We recommend you consult with your installer for exact maintenance requirements before you commit to installing a solar PV system. It’s also worth mentioning that a reputable installer will provide you with good quality products they know will last the distance, as they are ones to be called back in the event of a fault.

Up above

Many installers now offer arrays that use self-cleaning panels.  These have a specialist coating which stops water droplets from sticking to the surface. Instead they roll off of the panels taking dirt and dust with them.

For existing micro-generators in the UK, our temperate maritime climate means that roof-mounted systems tend to be self-cleaning. This is because rain-water washes away the majority of the dirt and debris that would otherwise accumulate on the panels. A good shower should even wash away leaves and bird droppings that may have accumulated. Cleaning only becomes more of a requirement if your panels accumulate a lot of bird droppings or debris, or in Mediterranean climates where there is little rainfall and a lot of airborne dust, meaning a layer of dirt will build up on the modules causing a drop off in generation.

Remember that the performance of solar panels does fall off gradually over their life time in any event so some reduction in output should be expected.  This degradation is usually highest in the first year (around a 2% reduction in performance would be normal) and more steady in the following years at less than 1% per annum.  After 25 years you should still expect your panels to be producing at least 80% of the electricity they generated when they were new. The data sheet for your solar panels will provide more information on this.

If you feel that cleaning solar PV is necessary and you feel comfortable taking on the task yourself, make sure to consult our guide which covers do’s, don’ts and safety considerations. If you’re looking at using commercial cleaning services, try and calculate whether the cost of cleaning is worth any increase in PV generation afterwards which is likely to be small. 

Down below

In most existing solar PV installations (before the invention of in-roof technology), a small gap exists between your roof tiles and your panels to allow space for electrical equipment and cables and to ensure your panels don’t overheat.

This inadvertently provides a suitable home for rodents such as the Grey Squirrel, and more commonly, urban bird species such as the Feral Pigeon (Columbia Liva). Pigeon droppings on and around your solar PV is likely to have a corrosive effect on your roof tiles, particularly on older properties. The area underneath the panels can also be damaged as a result of nesting, as Pigeons can dislodge wiring and even stop the solar panel system working altogether.

We suggest that the best way to avoid the issue is to ask your installer what you can do during the installation process, in order to avoid becoming the neighbourhood Pigeon hub in the first place.

For existing micro-generators, there’s a whole host of pest control companies out there offering their own solution to the problem. However we suggest that you check first whether any attempt to remove Feral Pigeons and any other critters from your rooftop will be done in a way that is legal, humane and not unnecessarily harmful to local wildlife – see our guide on how to deal with pigeons under the panels.


Do you clean your solar PV panels? Take our 10 second poll to let us know. 
ThIs poll has now closed. 


More information about Solar Electricity on YouGen.

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About the author:

Sam has contributed to our blog since 2016 and previously worked for the National Energy Foundation.

He became interested in green energy after completing a degree in Geography (BSc) at Royal Holloway, University of London. 

Sam is passionate about renewable energy and is committed to spreading the word about the role it plays in delivering environmental sustainability. 

If you have a question about anything in the above blog, please ask it in the comments section below.

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5 comments - read them below or add one


dee1kanbiComment left on: 31 October 2018 at 5:39 pm

I have 4kw system on a flat roof of my garden annex and had installed it in 2013. Since then i myself have always cleaned my panels  3-4 times a year until now. I can not tell if my system is under performing or not but the system has now been paid off from the FIT this year. Cost of the system was £6000, rate was 15.44p and FIT has paid it off this year 2018. 

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Ben Whittle

Ben WhittleComment left on: 31 October 2018 at 1:28 pm

Deeppurple - I would have to disagree. There is a +/- 5% variation in annual performance and even greater based on monthly variations. Keeping track of loss of performance is actually very difficult unless you can take solar insolation and temperature etc into account which is beyond the ability of most people

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Ben Whittle

Ben WhittleComment left on: 31 October 2018 at 1:26 pm

I have looked into this.

If you assume a loss of 1% drop in performance year on year based on dirt alone (not degradation) - and I have to confess this is a pretty random figure but seems reasonable to me - then it is worth cleaning every year or every other year if you are on the highest tariffs from 2011.

After that the cost benefit changes so it gets progressively more difficult to justfify. From 2014 every 3-4 years is financially justified. It does of course depend a lot on what the cost is to get it done.

Of course we should all clean them yearly if they are easy to access - money isn't everything!

Ben - 



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cannonballdazeComment left on: 26 September 2018 at 11:45 am

How about about cleaning them when It's raining with a soft window cleaning towel attached to a long pole - as sold in Aldi ?

Cheers - Joe

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deeppurpleComment left on: 26 September 2018 at 11:32 am

As with most PV system performance issues the best way to decide whether to clean or not, apart from the obvious visual check, is to keep a monthly log of panel output and compare this with predicted output of your system.

Excel spreadsheet with graphical display of the readings works well and it is very easy to spot if your panels seem to be underperforming.

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