Is Solar Panel Cleaning A Waste Of Time And Money?

a bird shitting on a solar panel

Solar Panel Cleaning – It’s A Dirty Job, But Nobody Has To Do It

The day your solar panels are installed is the day you will get the best performance out of them.  After that it is all down hill. Admittedly, it is a very shallow hill and it might take over 40 years to get to the bottom, but day one is going to be as good as it gets.

One of the reasons for this is dirt. As soon as your panels are out in the open in the clean air, or not so clean air, dust will start to settle on them, blocking sunlight, reducing their efficiency, and costing you money.

The obvious solution is to pay someone to clean those panels, or get out there and clean them yourself. And sometimes this obvious solution will be a sensible course of action. If a dust storm has covered your panels in dirt or pelicans have had a poop party on your roof, then it’s a pretty good idea.

But most of the time solar panel cleaning is not worth it.

Because the average increase in output from cleaning panels is usually small, taking into account the time and risk of injury if you do it yourself or how much you will need to pay to have it done, under normal circumstances it is not cost effective.

It makes far more sense simply to install a slightly larger system to compensate for the minor loss that results from grime than it does to pay someone to clean them.  Or if your system is already installed, spending money on energy efficiency is far more cost effective than paying people to clean your panels.

Normal Grime Hardly Affects Solar Panels

Dirt on solar panels usually has very little effect on their performance.  This is because, for most homes in Australia, rainfall is enough to keep solar panels reasonably clean. Grime will build up, but eventually there will be sufficient rain to wash most of it off.

Cleaning in addition to what is done naturally by rain will boost panel output, since on average they will have even less dirt on them, but it doesn’t help much.

A study done in the United States in Tucson, Arizona, found that cleaning solar panels only improved their output by around 1%. This is in a location that only receives a little more than half as much rainfall as Adelaide, which is Australia’s driest capital.

This doesn’t mean that in your particular location cleaning panels will only improve average performance by 1%. You might happen to live in a dirty, dirty place or have lots of birds trying to turn your roof into the site of a future guano mine. But I would estimate that for most households in Australia, cleaning solar panels twice a year would only improve their average output by around 2%.

Flat Panels Are An Exception – They Need Cleaning

Rain will wash most of the filth off panels, but only if they are at an angle. When solar panels lie flat water can pool on them and have nowhere to go. Eventually it evaporates and leaves grime behind. Worse, things such as leaves and other debris can land on solar panels and just stay there and seriously affect performance. A thin layer of grime will let most light pass through, but a leaf is specifically designed to capture light. After all, it is a naturally occurring type of solar panel.

To avoid these problems, and because it is bad to have any electronic item sitting in water for an extended period of time, it is a very good idea to put solar panels on flat roofs in frames that tilt them at least 10 degrees. I recommend east-west tilts for a flat roof – where possible.

If your panels aren’t tilted then you’ll have no choice but to clean them if you want to keep their performance up. Google found that while cleaning their tilted solar panels wasn’t worth the effort, cleaning their flat ones after they got particularly dirty could double their output.

Don’t Be Fooled By The Cool

You may may have heard people claim when they clean their panels it improves output by 10% or more.  And they may be right. Some people live in filthy, filthy places.  But it is easy to be fooled into thinking that cleaning panels has a greater effect than it does.

Firstly, cleaning panels will cool them down and cause them to operate more efficiently. If someone cleans hot panels when and immediately checks their performance and sees it has increased by 10%, that could be entirely due to the fact they are now 40 degrees cooler.

And even if you aren’t fooled by the cool and do get a significant, real improvement in performance, as soon as they have been cleaned those panels are going to start getting dirty again, so the average increase in performance from cleaning will be considerably less than the immediate increase that results.

Solar Panel Cleaning Costs Money

Professional solar panel cleaners insist on being paid for their services.  It doesn’t matter how much you bargain with them, they always refuse to do it for free.  Even my own children expect me to pay them money to clean solar panels and if I forget they’re up there and put the ladder away, they ask for hush money not to tell my ex-wife.

The amount of money you will be charged varies on where you live, how many storeys your home has, and how many panels you have to clean.  A reasonably common price is around $7.50 a panel for a one storey home or $10 a panel for a two storey home.  But they do have a minimum charge, so if you only have 4 panels don’t expect to get them cleaned for $30.

If you shop around you might be able to find someone who will clean your panels for under $5 each.  But note that less professional cleaners might be more inclined to make a mistake such as flushing a load of soap suds into your rainwater tank.

The Economics Of Paying For Solar Panel Cleaning Don’t Pan Out

Paying people to clean your solar panels costs more than it’s worth.  Even in a situation that is as close to being best case as is realistically possible.

Let’s say you rescue a panel cleaner’s poodle from drowning during the great poodle flood of ’07.   As a reward she gives you a great deal on cleaning panels, only $5 each, and you pay her to clean them twice a year.

Your rooftop solar system is 5 kilowatts with 20 panels.  It’s in a sunny location that, without cleaning, generates an average of 25 kilowatt-hours a day. You have a 44 cent feed-in tariff and because you are never home during the day you receive it for every kilowatt-hour generated.

If solar panel cleaning twice a year results in a 2% increase in average solar generation, then you will earn around an extra $80 a year, but you will have spent $400 having your panels cleaned. So even under excellent circumstances it makes no financial sense.  Even if having your panels cleaned twice a year increased their average output by 10% a year, which is extremely unlikely, you would only just break even.

Because the above situation is about as good as it can get, most people will actually be far worse off. For example, a Sydney household with a similar sized north facing system that has a 6 cent feed-in tariff, self consumes 50% of the solar electricity they generate, and pays 25 cents a kilowatt-hour for grid electricity, would only save approximately $21 off their electricity bills each year if cleaning results in a 2% increase in average solar panel output. So there is really no way having your panels cleaned can pay for itself.

Cleaning Panels Yourself May Not Make Economic Sense

Paying someone to clean your panels doesn’t make economic sense, but what about doing it yourself? That has to be cheaper, right?  Well, that depends on how valuable your time is to you and what value you place on your own neck.  Or at least having a neck that functions as it is supposed to.

Let’s say you value your time at the Australian minimum wage of $17.70.  If it takes you 20 minutes to clean your panels, doing it twice a year will cost you about $12 worth of time. As a 2% increase in output can save someone with a 5 kilowatt system over $20 a year, cleaning panels yourself can be worthwhile.  But this calculation leaves out a major cost and I am not talking about water or detergent.

Each time you climb up on your roof, or use a ladder to spray water onto your solar panels,[1. Update 13 Jan 2020: If you are going to spray solar panels with water, don’t use a concentrated high pressure stream, as this could potentially damage the seals between the glass and the aluminium frame.  Ideally, you want the water to fall on the solar panels like rain.  Thanks to Richard for pointing this out in the comments.] there is a small but real chance you will fall off and injure or kill yourself. If you value your life at $10 million and you think there is a one in a million chance you will accidentally kill yourself each time you clean your solar panels, then pricing in that risk adds another $10 each time. This means cleaning you solar panels yourself may not pay either, provided you place a high value on your own life.

But if you clean your panels just by spraying them with a hose from the ground, you are probably not in any great danger. You are very unlikely to accidentally strangle yourself with the hose, or experience a sudden surge in water pressure that kills you with exploding rubber hose shrapnel.

Don’t Clean Panels – Install A Larger System

Installing a slightly larger solar system to compensate for losses from dirt costs less than paying someone to clean panels.  One extra panel on a 20 panel system increases its output by around 5% which is more than twice the average loss I would expect from not cleaning them.  Installing a system one panel larger will definitely cost less than the $600 or more it could cost to have your panels cleaned 4 times.  One extra panel can more than compensate for loses from dirt for the entire life of the system.

While adding panels to an existing solar system is often not practical, there are still plenty of things people can do that will save them more money and have greater environmental benefit than paying for panel cleaning.  For example, they could invest in insulation, LED lighting, a heat pump hot water system, or buy a bicycle and use it for some trips instead of a car.

If You Want Pay For Clean Panels, Please Go Ahead.

If you want to pay to have your solar panels cleaned, please go right ahead.  Don’t let me stop you.  Just be aware that most of the time it will cost more money than it is worth.

I have no desire to put solar panel cleaning companies out of business, so if you decide against having your panels cleaned, please consider hiring them to do something else you will find worthwhile.   For example, some solar panel cleaners also do windows.

For those interested in cleaning their solar panels themselves, regardless of whether or not it makes economic sense, I will write an article on the best way to go about it very soon (added: view Ronald’s article on how to clean solar panels here).

About Ronald Brakels

Joining SolarQuotes in 2015, Ronald has a knack for reading those tediously long documents put out by solar manufacturers and translating their contents into something consumers might find interesting. Master of heavily researched deep-dive blog posts, his relentless consumer advocacy has ruffled more than a few manufacturer's feathers over the years. Read Ronald's full bio.


  1. Jack Wallace says

    We’ll have to stop meeting like this, young fella!
    There was an ancient piece of wisdom to the effect that if you wanted any job done as quickly and easily (ie ‘efficiently’) as possible, give it to the laziest man you know.
    The solution to cleaning solar panels ~ and at the same time encouraging the ….er, ‘smart-arse’ (splurt!-arsed??) magpie to seek less feather-ruffling targets ~ is to crank up the old fire-pump and let fly from the comfort of your lawn.

    Not only do you get rid of the bird and the shit, you actually recycle the water by way of flushing out your gutters and watering (along with fertilizing!) your gardens at the other end of the downpipe.


  2. Hate to be pedantic, but houses don’t have ‘stories’ usually, but they can have ‘storeys’. At least I think that was the case when I was a young fellow at school.

    • Ronald Brakels says

      I am so, so sorry for you, ramjetski. You hate to be pedantic? I can’t even begin to imagine what that must be like. You have my condolences.

      And thank you for pointing out my spelling error. It’s all fixed up now.

      • Don McNulty says

        Hi Ronald,
        I would like to disagree on solar panel cleaning. I have no panels of my own & I’ll bow to your research on output. My expertise lies in the science of cleaning. When I clean my kitchen counter daily it takes but a few minutes. When I clean the kitchen counter inside a hoarder’s home if less Sq. Ft., it will take an hour or more. Why is that? All soiling & contamination starts with bio-film. If you don’t regularly remove the soiling all the way thru the bio-film it will continue to build more rapidly to a point where I’m sure the efficiency of your panels would be great effected.
        Then your cost of cleaning will be higher.
        If you’ve washed your car at a self-service car wash with a power sprayer and taken it home to wax it. Once you start waxing you notice there’s yet one last layer. So you break out a bucket a sponge and wash rinse and then wax. That last layer is your first layer of bio-film. Exterior bio-films are usually made up of carbon, latex, bacteria and other micro-pollutants such as pollen, silica, insect parts, skin, hair, lipids, and others. Soiling happens in layers. The more layers the harder to remove.
        If you’ve written any articles on UVC lighting inside HVAC system to disinfect the air no one I’ve seen ever mentions a regular cleaning cycle of the UVC bulb.
        Bio-film is everywhere especially in the human environment whether interior or exterior. You see it best in two areas. First the tartar on your teeth is biofilm, secondly, the grunge around a light switch, door knob and cabinets.
        Well you have a great week that’s my sermon of the day.

        • Biofilm or not, washing in areas that receive regular rain doesn’t pay – or even make sense. There are peer reviewed scientific trials quoted on this thread that back that up. None of them mention biofilm. What you might think and your anecdotal experience carries little weight. Is there any trials you can quote to support your claims?

        • Reg Watson says

          If your panels can attract dirt and contaminants that are not completely washed away by rainfall and you clean your own panels, are not foregoing a certain level of income in the time it takes you to do so, and you don’t fall off the roof in the process and kill or severely incapacitate yourself) then clearly the justification for cleaning your panels to get them as close as you can back to the original “just installed” condition can only be beneficial to the power output – and even more so if you live in a dusty low-rainfall area or are prone to bird droppings or lichen.

          Yes with the costs of labour these days it is probably not “cost-effective” to pay someone to do it versus the cost of increased output and even doing it yourself is hardly going to make a huge difference to your power bill. But logic tells me that if you are happy to do it yourself at no cost and get away from the troubles of ground-dwelling world issues for a while and instead pottering happily up on the roof enjoying a great and legal view of the next-door neighbour in her bikini, it can only be a small but beneficial thing to your pocket and mental state.

    • Jack Wallace says

      Presumably you went to school in SA….or QLD.
      And just for the record:- small investigations often reveal stories in and about houses.
      ….though it really is impossible to knit picks.
      ….or even pricks, according to Shakespeare

    • Thank god someone else knows the existence of this word! I thought I was going mad! Storeys not stories!

  3. Jack Wallace says

    hehehe…..Meanwhile, in SA ~ and soon to be coming to a power-grid near you ~ a bit of a storm (which storms are slated to become more frequent and ferocious with global warming) has wiped out power supplies and therefore water-supplies and sewerage-disposal, etc..
    Except for those non-trendy luddites who decided to go Stand-alone and DIY before the….er, shit hit the cumulonimbus cloud. Their supplementary wind-turbines will be churning out power like a politician does promises!

  4. Paul Rosato says

    Mr Brakels, although there are a number of points in your article we could have a healthy debate on all day, (considering my profession is inspecting and cleaning solar panel systems), your guidance to readers on the hazards of working at heights and the risks associated with having someone other than a professional provide solar panel cleaning services is extremely wise!

    There is certainly a lot more at stake (life/injury or system damage) under these circumstances.

    Thanks for your insight from the other side of the coin.

  5. I’ve just cleaned my panels this afternoon – first time since they were installed 8 years ago. Peak output is 1.9kW on a 2.2kW system in the middle of Summer with a maximum 15kWh generated during a sunny day. Not sure if that’s a normal attrition rate for the age of the panels.

    No brainer for me to do as I was already cleaning the gutters. Will see if performance differs tomorrow but the panels are noticeably cleaner.

    • Cleaning was worthwhile. Averaging around an extra 2kWh per day with the most increase being when the sun is low in the sky or overcast conditions.

  6. warren Harvey says

    I’ve always cleaned my panels about every six months since they were installed 15 years ago and to that end, placed the panels on a separate frame built low down so that the panels were easily assessable. Luckily I suppose, I had the space surrounding the house, to do so. I cannot believe how dirty the panels get sometimes, particularly after a long dry spell of weather when the panels are prone to get covered in dust. Then there is bird poo which sometimes covers several individual cells at the same time, adversely affecting a panels performance overall. NOT cleaning this muck off on a regular basis entices lichen to grow upon the glass surface of the panels, which further affects the panels performance. I’ve seen a few panels on older systems, belonging to people who have not taken the time to clean their panels, where lichen had covered almost the whole panel. I’ll continue to clean my panel’s on a regular basis thanks and advise anyone installing panels for the first time to consider cleaning them as an important part of solar power management.

    • Grace du Prie says

      How do you clean them?

      • Hi Grace…. After the recent dust storms we experienced and no follow up rain, the covering of dirt on our panels became quite evident so it was time to give them a clean. I find it necessary to do this about every 12 months on average, regardless of rainfall – more if they appear to get bird poo on them or they get covered in dust. We rarely get any help from the rain to keep them clean anyway because we get so little where we are.

        I don’t take too much notice of those who say cleaning them doesn’t improve performance or is necessary. For the most part, I simply do it to satisfy myself that I’m getting the best possible performance from my panels that I can. Without going into figures, (too technical for me) I do see a small improvement in their output after cleaning, (according to the regulators) – and that suits me fine!

        When I do the cleaning, I begin in the morning whilst the dew (if any) is still on the panels. This seems to help loosen any grime or lichen etc. on the panels, which makes for easier removal of the same. I can access our panels from the ground (for personal convenience) They’re erected on their own separate built framework angled at approx. 27 degrees – not on a house roof.

        I connect up a hose and again wet the panels down thoroughly, then brush them down with a long handled window cleaning brush which I purchased from a window cleaning supply shop. I don’t seem to require any detergent for cleaning – just clean water seems to do the trick.

        It isn’t as easy to do as it used to be because the system has been extended over time and I now have to fully extend the brush handle and reach out and over to the top-most panels. It does the job very well however. Once I get one string of panels brushed, I hose them off and move onto the next section.

        Should panels be installed on a house roof, I would imagine the job of cleaning would be a lot more difficult, but in essence, the method of cleaning would need to be similar. You would need to plan to get onto the house roof each time when cleaning required it. However, if your physic and age – like me – are not quite up to the task of getting onto the roof, then you may just have to trust that the rainfall in your area is enough to do the job of cleaning the panels for you.

        Either way, I wouldn’t stress. My neighbour installed their solar panels on their house roof at the same time and they don’t seem to have had any issues with keeping them clean…..they simply don’t do it! Hope this helps. Cheers.

        • Grace du Prie says

          Thank you so much! We have twice paid someone to clean the system. However, since my husband (72) still goes on the roof to clean the gutters I feel he should have no problem cleaning the panels. Since he is still working as a house painter too he has no problems with ladders and height. I just was not sure how to go about it. So thank you for your info on how to do it! That is saving some money again. We have 14 panels on the roof. Oh and…living in Ipswich Qld we hardly know anymore what rain is! We seem to go from drought to drought with once in a while a flood in between. 🙁

        • Richard V Anthony says

          Unless you live where it rains every day there shouldn’t be any question about whether you should clean them or not but how? IF you can access them safely and use tap water and a brush you will definitely get a lot of the soiling off from them, the problem there is how do you dry them? If they air dry the minerals in the water dry on the glass and little by little make the surface rougher and more susceptible to hold dirt going forward. Like washing your car, if you can dry it before the air does it’ll be fine but that usually isn’t possible. We use deionized water so there is not residue of any kind and they dry completely spot and streak free. Pima County, AZ

          • Grace du Prie says

            That is good advice, thanks. We have a water filter on our tap (5 stage reverse cycle) so I’ll tell hubby to use that water and then dry it straight away!

        • Rob Maddux says

          This is from an experienced Solar Tech Engineer

          “As soiling concentrates on the solar panel, the losses attributed to this factor increase on a monthly basis and could lead up to 30 % annual losses (and even more in extreme cases). Therefore, it is necessary to develop a maintenance routine in order to maximize energy yields of solar panels and to keep soiling losses around 2% – 5% annually.

          If you search solar panels cleaning there are claims that loss of efficiency from having dirty solar panels is very minimal but I experience a gain of 25% on average and I clean them 3-4 a year.
          That increase is not just on that same day they are cleaned which cooling off the system may cause an increase in electricity generation, I check them the day before cleaning and the following 4-5 days after cleaning at the same time of day and with the same weather conditions. Cleaning is very beneficial from my personal experience

      • I have solar cleaning sprinkler system. It is very low cost and fully cleaning panale for 3 minutes

  7. I was told to get my son (Plumber) to clean my panels once every 12 mths but not to worry for first 18 mths. I receive email every month to say my system is performing at 100 % so after 12 mths since they were installed I’ll leave it till the 18 mths are up . Love that my electricity bills are so low.

  8. Well thats all fine , have your panels set up under powerlines or a antenna , trees and they will be filthy in no time, or lichen can even stain solar panels ! So i say better to be safe than sorry they weren’t
    Given a once a year clean!

    Can also depend on where you live!

    At the end of the day it comes down to consumer choice!

  9. Scott Meloni says

    I often clean my car as “the rain” doesn’t seem to do what you say it does “clean glass” and as for if it is worth it! Aren’t solar panels an investment? Don’t cars need a service? Doesn’t the Warranty tell you what is needed?

    If your paying a solar cleaner more money than you are getting back then. No it’s not worth it! But if your solar cleaner can show you an improvement of 10-20%+ then do your maths!!

    • Finn Peacock says

      Hi Scott,

      How do you demonstrate an improvement of 10-20%, and how does that compare with what you charge?

      Best Regards,


  10. Total waste of time cleaning solar panels. Repeated trials have not demonstrated any measurable improvement.
    Claiming a 1% difference is a joke as there are too many other factors involved for this to be significant.

    • I beg to differ – if it works for Google…. ! Following is not my work but have put the link to Google’s own blog for the sceptics.

      Google conducted a groundbreaking experiment at their 1.6 MW solar farm in Mountain View, California. They found that cleaning the solar was “the number one way to maximize the energy they produce.” Cleaning solar panels that had been in operation for 15 months doubled their output of electricity.[1]

      The same study also found that rain is not a satisfying way of cleaning solar panels. Solar panels that were cleaned professionally had a 12% higher output of electricity compared to those cleaned by rain.

      • Not quite . Maybe you should have read the study properly before misquoting their findings.
        It clearly states that there is no advantage in cleaning solar panels that are installed on an angle. So that would include all panels installed in Australia.

        So my original claim is supported by the study you cite. Hopefully most people will realise this and stop paying for a service that has not benefit.

        Nice try Adam.

        • I don’t argue that there is some cleaning effect with rain Brian but not everyone can afford to have their panels installed on an angle – eg if they have a flat roof. And I can tell you my panels (that are on a good angle) definitely do not fully “self clean” in the rain and I live in Tassie where the air is probably cleaner than most Australian States. In addition to a dust film, I get tree-leaf sap and bird crap.

          I guess you never clean your car either because it always gets cleaned in the rain ? Try having a look at the side doors (which will be almost vertical) when it dries after a rain storm !

          As far as I am concerned with solar every little bit I can squeeze out of it the better. I would not pay to have my panels cleaned but am happy to get up there and do it myself for free.

          • Richard Anthony says

            One little known fact is that their 100% is likely somewhere around 90% of what they are actually capable of. They don’t want to have to argue with people about whether their panels are achieving the promised output.

          • Richard V Anthony says

            I suggest you evaluate the “self cleaning” with rain proposition the same way you evaluate how well the rain washes your vehicles or the windows on your house. Just because it knocks some of the dust off is not to say they are “clean”. Another mistake is to spray tap water on them (unless your water supply is mineral free) because when the air drys them the mineral spots will stay and gradually become more adept at holding dirt; downward spiral.

    • Richard V Anthony says

      That’s just not true. Most of our customers see somewhere in the neighborhood of 10% increase in production. What can’t be demonstrated at this point is how much faster they will degrade if left dirty. Solar likes light but not heat. The dirtier they are the hotter they are and the less they produce. Studies have shown that for every degree the panel goes above 107* Fahrenheit you lose 1.1% of production. 107* isn’t hard to hit, that can happen on an 80* day. We use deionized water, no chemicals, and suggest twice a year cleanings as more than that will probably not return the cost of the additional cleanings.

      • Ronald Brakels says

        Panels in Australia don’t do that. I would have noticed. A typical panel loses about 0.4% of output for every degree Celsius above 25.

  11. What if the day the solar panels were first installed was heavy overcast but day two it was sunny; which day then gives the best performance out of them? That is why I get out there and clean mine every second day and even though performance will not equal results of the first day it will at least perform equivalent to day two which is always greater than nothing performed on day one.

  12. Last I checked, 20×5 =100 x 2 = $200….??

  13. Steven Winfield says

    Where did u learn all the B.S.above. You obviously don’t have solar but you would like to but you don’t have the money. I have had panels for 8yrs now and have not paid a power bill yet and I get an increase in output of 32 percent after cleaning. You sound like someone who doesn’t clean his car ever cause the rain will do the job you Richard Cranium. Don’t talk shit until you know what you’re taking about, that is factual.

    • No good getting angry at me. I’m just quoting results of several scientific trials, including the Google one quoted above, that clearly state that for panels installed at an angle (which should be all panels in Australia) there is no significant improvement in their performance if they are cleaned.

      Which is backed up by my own experience with the 90 odd panels that shows no measurable improvement after cleaning.

      Feel free to keep wasting your time cleaning (or money paying for someone else to clean) your panels if it makes you feel good.

    • You must live in a very dirty and polluted area to get a 32% output improvement after washing your solar panels. Either that or your mathematics is somewhat awry. Can you prove your claims??

  14. Try this report on for size Brian ! If you can accept that your panels’ output may have degraded by even as little as 1% due to the effects of dust/pollution etc that the heaviest rain can’t get rid of then that is still a fair amount when multiplied across your stated 90 odd panels – and that is a direct loss to your hip pocket, day after day, year after year.

    Still each to their own. Some of us don’t notice TV interference apparently. As for me, I can’t stand a degraded picture.

  15. I can accept that my panels may lose even more than 1%, especially when it hasn’t rained for a while but it still doesn’t make it worth it to clean them. Even when we were getting 60c/kWh gross it didn’t pay.

    Let’s say you clean them once a quarter: The best quarter possible for me would be 50kWh per day for 90 days (that would mean 90 cloudless days on the north coast of nsw – mpossible but exaggerated to make my point). That amounts to $30 per day. For 90 days is $2700. If they have been working at 1% less due to dirt I have lost $27. Hardly enough to justify me getting up to clean them and certainly not worth paying someone. Still not worth it at 2%. So In the current market with net metering it is even less viable to clean panels.

    Any study that claims a 1% improvement in efficiency after cleaning would struggle to show that 1% as statistically significant because there are dozens of other variables that can’t be controlled. The google study just confirms it.

    I’ve tried with my panels, unable to find a difference in output before cleaning and after cleaning on a couple of occasions, and that’s what sent me looking for results of research.

    The only point of note in the study you linked is the removal of bird droppings, lichen etc that may shade a portion of the panel may be useful.

    This study suggests that in areas where rainfall is low or for large arrays it might be justified. And other studies suggest in highly polluted or dusty areas it might be justified but most of Australia doesn’t fit that category.

    Even this study shows an 18% reduction but only when the entire surface of the panel was smeared with mud nearly 50u thick.

    So I’m happy to moderate my “don’t bother cleaning under any circumstances” to “if you live in a city in China or India, or if the flying foxes keep shitting on your panels or if someone is smearing mud all over your panels you better get up there regularly and clean them”.

    Not sure that applies to many of us in Australia.

  16. Thanks Brian – this certainly is an interesting issue with people firmly entrenched in both camps. I do know that one of my panels is right under the TV antenna and is currently covered in bird poo. I’ve bought a plastic eagle to fly above the TV aerial and will install it to see if that keeps the little beggars away.

    I know this is somewhat off-topic but as we are talking panel (in)efficiencies I noticed a YouTube video the other day where it showed how you can get a reasonable increase in power output when the sun was reflected onto a test panel with a mirror. It got me thinking that there is a small fortune waiting for someone to come up with a substance, film or whatever that can be painted/applied onto existing panels that has minute particles in it that can reflect additional sunlight downwards onto the photo-voltaic material underneath the glass – even better, perhaps nano-particles that can adjust to follow the sun around and keep reflecting light at the optimally correct angle !

    Maybe Finn Peacock should have stayed with CSIRO a little longer !

    • Adam, I have panels directly under my TV antenna and they are still free of bird shit 12 months on.
      I used different lengths of cable ties on the antenna rails pointed vertically to discourage birds from landing. So far sparrows, doves, black birds, magpies and spangled drongos all fly past my antenna to rest on the neighbours!

      • LOL – thanks Andrew – may give some cable ties a try – many thanks for the suggestion and a lot cheaper than one of those plastic spikey things from Bunnings !

        The plastic eagle kept falling down and getting tangled in the aerial in strong winds and I couldn’t find an easy way to attach it higher than the antenna so it would appear menacing to any bird wanting to roost under it.

        You’ve reminded me to get up and clean the existing crap off and will try some cable ties whilst I am up there !

  17. We’ve had the solar panels cleaned professionally once; mounted on a very high 3-bay shed; may not make any difference in output as neighbours tall trees cast shadow from 2 pm in summer. Biggest problem is cleaning the gum leaves from under the panels. Suggestions? Thanks.

    • Ronald Brakels says

      There is mesh that is used to stop animals from getting under solar panels and chewing on wires. That might stop gum leaves getting under your panels, although they might just pile up against the mesh.

  18. Brian Elvery says

    Leaf blower.

  19. I can only comment on my own experience which shows cleaning does make a material difference.

    Prior to cleaning the peak in our system was about 4.75kw each day. After cleaning, the peak was over 5kw each day, the same as when installed.

    I was prompted to clean the panels as I kept noticing the peak decline over time. Our system is just over one year old.

    Thankfully I followed the instructions in the article and cleaned early in the morning.

  20. I am wondering does the maths work out better cor a cleaning every few years? Would a panel clean at 10 bucks per panel or so every 5 years be worth it. I guess not if the improvement is only ever at 2percent. Still, we are in the far north and so mould that will not easily wash away may slowly potentially hinder panel performance. My system is going great and we overbought to ensure cleaning was not essential but now thinking about a clean.
    I was also noticed small cracks in the silicon, is that likley to be a problem? When i say small i mean up to 5cm or so.

    • Ronald Brakels says

      Generally filth does not build up on solar panels thanks to rain, so I wouldn’t expect a clean after 5 years to make much of a difference, but it will depend on your personal circumstances. If you can see your panels are building up grime that isn’t being removed by rain then a professional clean would be helpful.

      When you say there are small cracks in the silicon, I assume you mean the silicon sealant. Hopefully it is harmless, but if the deterioration becomes severe you can inform your installer. Or if you prefer you can directly contact the manufacturer.

      • Richard V Anthony says

        Terrible advice. No pressure washing is advised, it breaks down the gaskets on the panels and may ruin them.

  21. hi have had my 2kw x 12 panels removed, and replaced with a 5.5 kw 20 panels
    set up the 2kw x12 panels had been on roof for 8 yrs. could not believe how dirty they were could scrape the dirt of with scrape blade. wiil clean them
    every 12 mths now.

  22. Hi All,
    Wow, there are some differing points of view in this arena. Happy to say I am on the pro side for cleaning panels. After all it is the business I chose to be in. The information that is used on my face book site is relatively up to date within the last couple of years, not ten years old, and either from white papers, scientists, or from personal ‘on the job’ experience. Not from individuals that have an opinion because they own a single solar system array. That is like stating that you have a motor vehicle and because it’s always worked perfect, all motor vehicles work perfectly. I don’t know about the eastern states of Australia, but in the southern metro areas of Perth, our panels do get dirty. Some filthy and some not so bad. There are some ideas on the nay side here that may confuse some people. By saying panels may never need to be manually cleaned, is in itself going against what many manufactures explain in their warranty manuals under maintenance. I prefer getting advise from manufacturers. (checking your own manual is a good thing to do.) Manufacturers also say to check earth wiring, panel attachment points and overall condition of wiring and panels, at least yearly. Now that’s all good for the people that are happy to climb onto their roof and check, and good on them I reckon. But what about the people that don’t? Not all panels are easily visible from the ground, so how do they know what condition their panels are in. No one here talks about hot spot litigation or soft/hard shading on solar panels, and how much damage can be done long term to panels with these issues. There is some talk of ‘add on’ diodes that help in shading, but in reality how many systems have had this done. Unless everything is explained to the purchaser about their solar system, or they have done their homework, and they are willing to pay the extra, they are in the dark on this subject. Lets be honest here, some people are not happy to pay to get their TV aerial shifted when solar panels are being installed, but if they knew how much power they lose from shading they may change their minds. Solar panel systems are the same as any long term investment. They need to be maintained to get get maximum longevity and maximum benefit. A yearly maintenance clean and check should be carried out, either by yourself or a contractor. If you would like up to date info on why you should clean solar panels, you are more than welcome to visit my face book page. Seabreeze solar panel cleaning services. But be aware, because some photo’s may show hard soiling of a lot more than 1%. All photo’s are of actual jobs done by me and not taken from other sites.
    Clean panels = efficient panels

  23. Edward Schoenhoff says

    You mention that panels work more efficiently when cooler,
    Can you do a cost/value breakdown, If you were to install a rooftop sprinkler system which would turn on every half an hour for 1 minute sprays.
    Would the reward of getting a higher Kw feed in outweigh the cost water used & initial installation.

    • Ronald Brakels says

      Hi Edward

      For every 10 degrees increase in temperature a typical solar panel will produce 4% less energy. That’s 4% less in total so a 17% efficient panel won’t fall to 13%. Instead it would be about 16.3%. Because good quality panels have fallen so far in price it doesn’t make economic sense to install a cooling system. It will always be cheaper to simply install more panels instead to make up for the losses. Even if you had maxed out the number of panels it is possible for you to install you’d be better off spending the money on energy efficiency measures such as more energy efficient appliances or insulation.

      Good quality panels have fallen so far in price there is no point in

  24. Yes, It’s all well and good to go on and on about a few dollars saved here or there, but there are other factors to be taken into consideration when contemplating having your panels cleaned.

    Fire hazard:- The amount of dry leaves and debris that I have cleaned out from under panels is frightening, even more frightening is the fact that the worst I have come across have been in schools.

    Rodent nests:- Nothing like having a rat run up your arm whilst your laying flat out on your stomach trying to get at the leaves from right under the panels. This leaf build up also seem to make great possum nests, bird nests and python snake habitats.

    Workmanship:- So many installers use nylon cable ties to tie there cables to the frame. These are not UV stabilised and simply fall off over time, leaving most of the harness laying directly on the roof usually amongst the previously mentioned leaf matter. I always replace them with stainless steel cable ties.

    System integrity:- Testing of the system from top to bottom to prove the system is operating within tolerances. I have been to many installations where the circuit breaker at the panels had tripped in the last thunder storm and the home owners were not aware that there solar system was not and had not produced a watt since then.

    Street appeal:- Filthy panels with a lot of moss growing over them just looks bad from the street. You have installed your solar system and feel good about going green. So why not keep the panels looking their best, just like the rest of your house.

    • No argument with the leaves, rats, cable ties, integrity, moss? (i think you will find it is lichen) and general health of the panels. The need to sort these issues is not part of this thread and there is plenty of reasons to do something about them.

      Back to cleaning panels.

      And the evidence (from several sources quoted in my previous posts) is that it is not worth the time if you do it yourself. And a waste of money if you can be talked/tricked into paying someone else to do it for you.

      How they look? Really?

  25. Hi Brian. I had to reply to you about your post. Do mind me asking what you do for a living? Are you a Seer, mind reader or time traveler? Because the majority of solar panel cleaners that I associate with, check and correct the points that Jeff is talking about in his post. I feel you have completely missed the point that Jeff is talking about, they all work together. It’s a thing called multi-skilling, or value adding and they are really easy to do together. For the majority of us, that’s what we do. First of all we are contacted to clean the panels. While we are up on the roof we also inspect the condition of the panels, check the wiring and have a look to see if there are any other issues in the area. And yes, if cable ties have broken and cables are freely hanging but still connected and coming into contact with the roof and have no damage, we correct that. If I see any damaged tiles or I damage a tile, I replace them. I notify the clients of the condition of panels. If the panels have spider cracks through them, photos are taken, info is written on the receipt and next time they are cleaned, a new report is done.

    Opinions are like arseholes, we all have one. But I would recommend that you make sure your opinion is backed up by some hard facts. As for the moss, you state that you will find it’s lichen. You were not there, so your opinion of that is baseless and has no justification, except for your own validity that you know all in this grand land. I have come across both moss and lichen growth whilst cleaning panels.

    Before starting out in this business I knuckled down, read a lot of research into the subject, as to whether it was viable for myself and to the client. The majority of scientific white paper testing that has been done, is overseas and done in a controlled environment, mainly dealing with different types of dust particles. Many of these state that bird scat and other environmental fallout were not part of these tests and there needs to be more scientific testing into these because outcomes would be extremely different. Sadly, not enough testing has been done in Australia. Some will argue that Australia is different to the countries where tests have been conducted, but with a quick check on the net, this is one comment:

    Australia is a land of extremes with temperatures ranging from highs of 40°C in the central desert regions to below freezing in the higher regions of the country’s southeast. Sometimes these extremes can be experienced on a single day.

    From its northern most point at 10° 41′ 21″S on Cape York to the southern tip of Tasmania at 43° 38′ 40″S, Australia experiences almost every climatic condition encountered elsewhere in the world, along with some that are unique. One of the most significant features of Australia’s climate is its long, hot and often dry summers.

    Understanding the above, it is comical how some people figure that because their panels are free of bird scat, lichen, moss and leaves, they have the belief that all panels are the same.

    It is only your personal assumption that solar panel cleaning is not worth the time to do yourself, or get them cleaned professionally. There is more than enough evidence out there to humbly accept that your statement is flawed. Sometimes people only read what is relevant to their wanted outcome. But I do take offense to being noted as a trickster and would hope that you have some good hard core evidence to back up that statement.

    As to your last comment, How they look? Really?
    I personally have never heard of this for solar panels, but people clean or get their residential windows, cars, boats, caravans etc cleaned for that very reason, of looking good and pay good money to get this done. Once again you feel the need to question Jeff for this comment, but again you have no idea of whether this is Jeff’s comment, or a reason that a client asked Jeff to clean their panels. Hence my comment, Opinions are like arseholes we all have one, but sometimes are they not worth listening to.

    To aid people in making their own minds up, here are some links that may help them.

    LG and Bosch are some of the leaders in solar panel manufacturing, and as such, have spent a lot of money on research and development in keeping solar panels clean, nano technology is at the fore front of this development. Even these two company’s understand the need to keep panels clean. But for all the R&D, they openly understand that their newest technology still needs maintenance cleaning and states this in their operating and installation guides.

    I for one would prefer to follow manufacturer guidelines, than comments from individuals with limited or no factual experience.

    For more info on solar panel cleaning visit my facebook site.
    Seabreeze solar panel cleaning. Located in western Australia.

  26. Jeff Chenault says

    I love the article and the like arguing comments that I can have knowledge for the some issues that I never encounter. I am grateful for the brilliant ideas you shared in here, I am looking forward to have some more ideas from all of you guys. Keep it up!

    • Ronald Brakels says

      A three person household in Sydney uses an average of around 5,400 kilowatt-hours a year. An electric car that gets 5.5 kilometers per kilowatt-hour and is driven the average annual distance for a passenger car of 14,000 kilometers will use 2,500 kilowatt-hours a year. So a home and an electric car will consumer roughly 7,000 kilowatt-hours a year. As a rule of thumb, one kilowatt of north facing panels will generate an average of around 4 kilowatt-hours a day. So 4.8 kilowatts of solar panels will produce around 7,000 kilowatt-hours a year.

      In other words, a typical household will need a 5 kilowatt solar system to provide electrical energy equal to the consumption of the home and an electric car.

  27. Paul Croskrey says

    I find blog to be fake news, why do I say that? The author obviously has no clue what reality is. Sunpower the largest solar panel manufacturer with the best product with millions of solar modules installed at schools, homes, commercial even utility scale installations where upto a million panels have been installed.

    Sunpower and many other companies like Tesla and SunRun, and thousands of homeowners which add up to many thousands of installations pay us to wash the solar panels sometimes 1 to 4 times a year. Even Google pays us to clean thier solar panels, The Apple building in Cupertino California with 20,000 panels are cleaned once a month. Apple tells us they get a 50% increase of production when we clean them once a month VS once a year. Losing 50% production is akin to having 10,000 panels not working. The lack of production creates demand for cleaning, the cost of cleaning is a investment that pays a return in power production that can add up to 3 to 4 times what it cost to keep them clean.

    This information the author is providing is for solar systems in drier desert areas where there is no dew set and therefore no dirt sticks to the panels. In areas like Saudi Arabia where they even use a giant truck mounted leaf blower to blow off the dust. This is a very small percentage of installations across the globe. To put a blanket comment that it does not make sense to clean solar panels is pure malarkey.

    Cost to clean residential panels is not based on how many panels there is.
    So to say someone anyone would clean 4 solar panels for $20.00 is not real. How can you own a truck pay for gas , have the right equipment , have the proper insurance and then get on someone’s roof for $20,00. We charge between $100.00 and $125.00 for a residential solar panel cleaning, Which covers using the right equipment, having insured workers earning a living wage. Our customers know you wont have issues if we break something since we charge enough to stay in business. Our repeat customers, thousands of them will tell you cleaning is about the most important thing you can do for your solar assets. Basically before you decide not to use a professional solar panels cleaner ask yourself, is it worth it to not clean your panels when you spent thousands to get em installed?

    • There is no evidence from scientific trials that have been carried out to show that cleaning results in anything more than one or two percent increase in energy production. Even if this was a statistically significant Improvement it is not enough to pay for the cleaning. Unless there are extremes like animal turds or sap from overhanging trees there is no scientific evidence to suggest that you should do anything more than make sure the panels are still in one piece.

      • Hi, Practical. Seems to me, you may only be reading research that validates what you want as an outcome. But I am more than happy to help you see some ideas from people in the know. I am sure that a senior scientist at Carnegie Melon University’s knows what he is talking about. please check it out at,
        I almost find it laughable, that the anti panel cleaning brigade struggle to find any unbiased evidence.
        Hopefully if you are an owner of a solar system, you would have bothered to read your manual, under the heading of maintenance!!! As I’m sure manufacturers also know what they are talking about.

        • Sorry but you have confused a comment by a researcher for a scientific study.
          It’s not research. You have quoted an opinion of one person and it hasn’t been tested. Even the title brings up a red flag – “Rain could make your solar panels dirtier, not cleaner”. Doesn’t say it does and nothing in the article suggests they have tested that hypothesis. The fact that it’s in PC World and not a scientific journal is another problem.

          A study takes many sites, repeats the experiment and collects data over a period of time then analyses the results using statistics. Like this . “Don’t hire someone to wash your dirty solar panels. That’s the conclusion of a study recently conducted by a team of engineers at the University of California, San Diego.” Yes, they found it increased output – but too small an amount to pay for the cleaning or justify you own time to clean them.

          Or this one: . Their conclusion? “Our data indicates that rain does a sufficient job of cleaning the tilted solar panels. Some dirt does accumulate in the corners, but the resulting reduction in energy output is fairly small — and cleaning tilted panels does not significantly increase their energy production. So for now, we’ll let Mother Nature take care of cleaning our rooftop panels.”

          Go ahead and pay someone to clean you panels but you are throwing money away or if you do it yourself find something else to do.

          What’s laughable is there are people out there trying to sell owners of panels a solution for a problem that doesn’t exist.

          Happy to read a study that can justify cleaning because I’ve go nearly 100 panels. And just for the record I’ve compared their output before and after cleaning and couldn’t measure any difference. Which is why I started to some research of my own.

          • Hi Practical,
            Thanks for the reply.
            Correct me if I am wrong, for I maybe a couple of rungs down the ladder from you on the intellect scale, are you saying that a researcher doing a scientific study is not research?

            I perused both of the links you supplied, so thanks for the reading. As I said in my first reply, I like unbiased evidence. Maybe you yourself failed to read the first link in totality, I have cut and pasted this for you out of the link.
            (But solar panels heavily soiled with bird droppings should be cleaned. That’s because the droppings essentially block all sunlight and will not be washed away when it rains. Engineers also found that at a few sites, photovoltaic panels were dirty enough to warrant cleaning due to very specific and localized circumstances. For example, being directly next to and downwind of a highway, factory or agricultural field may generate enough dirt to warrant cleaning.) By the way I am unsure about August 2013 being recent.

            I fear that for the second link you may have fallen on your own sword here, only because as you have stated, that if it’s not from a scientific journal it’s a problem. Your second link is from a 2009 google blog, now that’s a long, long, long way from a scientific journal, is it not.

            Was it worth me reading both links though? yes it was.

            You are incorrect in saying that I am quoting the opinion of one person, all I have done, is shown you and others, that enjoy this blog, a link to some information, far from a quote I feel. I understand and believe that you have a solar array and for you there is no reason for you to clean them, that’s great and I am sure that some people may be slightly envious of that. But putting a blanket statement of no solar panels require cleaning is unrealistic. After all, your only one man making a one off personal statement.

            I am not here to change peoples opinions, but to give realistic input into this blog, something of which, some people struggle to achieve.

            For myself seeing is believing, and I for sure believe.

          • Darrel. I mentioned cleaning due to unusual events like bird droppings/ bat droppings (in my area) in an earlier post. And yes it is justfied. The blog is not a scientific journal but the study it quotes was carried out using scientific method. Point is cleaning is not economically justified in most cases. Read the post from Ronald that introduces this thread.
            The essence of the studies is if you want to clean your panels go ahead but don’t try and kid people that it is necessary or economically viable at the feed in tariffs we get.

      • Paul Croskrey says

        Practical says, no need to bath for your skin will flake off as nature intended.
        I read a scientific paper written by deodorant companies who claim you don’t need to bath all you need is our product….get real Practical I am sure at least, I hope you bath at least twice a week.

        So you actually think science prepared and paid for by utility companies is worth reading let alone real science. The facts are solar panels do need to be clean to work at thier best performance. Utility companies even pay universities to do research and when it shows anything the utility companies don’t like they squash the reports. I can say they have been somewhat successful in brain washing some folks to believe they don’t need washing. I did get a call from one person out of thousands who wanted to argue with me about the return on investment and quoted one of those fake news reports. I told him go ahead and dont clean them and see for yourself. I told him to call me back when he come to your senses. Six months later or so he called and asked me to inspect his system telling me something must be BROKEN since production is very low. As I assumed it was so dirty no amount of rain would clean it even if it did rain in MAY. which it doesn’t do very much around here.

        When I told him it’s just dirt and did he want me to wash them he said a resounding YES. When I charged him $150.00 he said he was paying over $600.00 per month in utility costs. Instantly his costs went below $100.00 per month and when it dipped three months later he called me again and paid $150,00. He also told me that article was full it and thanked me for being patient with him. He also told me that $300 he spent saved him over $400 per month for the duration of the summer until it did rain again. $300 saved him $1200.00 in utility costs. So think about it how many folks who own solar read that fake news and act upon it costing them hundreds and possibly thousands of dollars that goes to the utility companies and its stockholders.

        Then someone like you comes along with no actual experience other then reading fake news and then acts on it like it is gospel. It just goes to show you that some people can be fooled some of the time and some can be fooled all the time. I do think people who own solar and somehow find this blog knows the difference between what Practical says and reality.

  28. Jack McFlackertyback says

    Why is the article based on cleaning twice per year and based purely on economics? How about cleaning every 5 years or so just purely to maintain them? Is the author saying they should never be cleaned?

  29. SolarEngineer says

    There are several factors to consider. I work in the solar industry as a performance engineer, and have analyzed soiling on carport systems in Southern and Northern CA at 5 degree tilt. They get absolutely filthy, and I have seen greater than 20% decreases in power output due to soiling. For example, after a professional wash, a SoCal (San Diego area) system’s peak output went from 108kW to 134kW, a gain of 24%.

    Other aspects which can benefit from clean modules are module degradation and long-term operation. Non-uniform soiling can accelerate module degradation, and if bird droppings are present, can result in accelerated module failure. It is most certainly site specific to determine what is the best route for maintenance or lack thereof.

  30. Hi Practical,
    Thanks for replying. It is enjoyable that we can have conversations of this nature.
    Here is a scientific review for you to peruse if you choose to.

    Its a long but good read that opens up on some of the grey areas on how some of the research is achieved. It has some very good relevance to the last link I sent you, that you so easily dismissed as having little relevance and no depth. After all, you said you went looking for research, normally a person searching for research, who has no bias, would not see any red flags, by just seeing the title.

    As you have stated, (“What’s laughable is there are people out there trying to sell owners of panels a solution for a problem that doesn’t exist”).

    You then state (that cleaning due to unusual events like bird droppings/ bat droppings (in my area) in an earlier post. And yes it is justified).

    Are you playing dirty politics here? Your saw want happened to Mr Turnbull when he tried to cover up the truth about the banks, didn’t you?

    It may be unusual for you, but not other areas. Australia has many different environmental climates.
    The quote below is from another scientific research that I can supply to you if you would like.
    Bird Droppings
    Bird droppings were frequently observed on every modules
    and were removed from the dirty cells. This was done because
    bird droppings were not part of soling loss studies and would
    jeopardize the entire experiment. If they were not removed
    carefully it would have ended in inaccurate results. A sharp
    tool was used to remove it from the modules carefully without
    scratching the surface of the solar cells. Initially bird droppings
    were creating a lot of problems. In order to keep
    the birds away from the solar cells metal spikes were placed on top of the solar modules in such a way that it casted no shade on the cell
    surface. The attachment of metal spikes on the photovoltaic
    modules declined the bird droppings to a great extent).

    One could say by removing the bird droppings off all test panels, it would render the whole research as a failure, as those areas have now been cleaned.

    One area of concern I have is with the second link you kindly attached. Even though they believe that sand in the corner of each panel is only causing small losses, the sand in the picture would be classed as hard soiling, which can cause hot spots on modules, and as we all know, this leads to premature failure of panels. Is this not another benefit for cleaning solar panels?

    Anyhow, as I said at the start of this little blog today.
    It is enjoyable that we can have conversations of this nature, that are based on both sides being truthful and of credible nature, why? Knowing from the very start it was you, Brian, running as an alias. Your ethics have now been exposed for what you are, a person that can’t be taken seriously for any of your blogs and you have the gall to call honest Solar panel cleaning businesses tricksters. You have now proved that you personally well and truly deserve that status.
    You are Practical by name but not nature.

    I hope now, that people who come onto this blog wanting to get fair and ethical feedback, now understand the tactics that some people go to.

    Just a little word of advise Brian, next time you want to play alias, change your AVATAR.


  31. Hi Adam,

    Yes it appears that Brian has dug a rather large hole for himself.

    As long as practical is the only alias on this blog, it would be sad, but not unrealistic if “Brian” could also be an alias.

    I suppose it’s up to Ronald, being the adjudicator of this blog, to decide whether to allow Brian to add further input into this blog. Outwardly “Deceptive” people should be held to account.

    Ronald is in a hard space though, because it appears that Brian, was his most loyal ally.

  32. Ronald Brakels says

    Sometimes I read through comments and think I must have written some horribly one sided, unbalanced articles when I was younger. But then I reread the article and I think — nah.

  33. If you want to get your panels cleaned go ahead but (long story short) genuine research (not my opinion, someone’s anecdotal experience or someone else’s opinion) is that it does not make ECONOMIC sense. Doesn’t mean they don’t get dirty. Doesn’t mean that cleaning won’t improve their output. Just means that in general the decrease in output when they are dirty isn’t enough to justify spending money or time to clean them. Because the increase in their output, at the rates we get paid for solar feed, doesn’t cover the cost.

    Doesn’t mean that panels never need cleaning. For panels with extraordinary dust, bird, flying fox, salt spray, dirt accumulated in the corner there may be an economic argument that favours paying to have them cleaned regularly – maybe every couple of years. I Suggest you do the calculations before forking out.

    To the respondents attacking the man not the message? I’m not trying to hide. If I was trying to “hide” under an alias I wouldn’t have referred to previous posts that i’d made.

    Wrt agreeing with Ronald Brakels? It is pretty hard not to. He researches his articles thoroughly and provides structured arguments. Unlike the respondents to my posts who attack the person and confuse anecdotal evidence with research.

    I can only conclude that the people who don’t like the message are those trying to earn a living from cleaning panels. No need to stress as there are plenty of gullible people around.

  34. I’m wondering if what you say applies in the tropics. My panels get a lot of mold and can be a bit hard to clean. I’m not sure if mold allows much sun through and I’m not sure studies in SA or the Nevada Desert are very relevant.

    • Ronald Brakels says

      I have seen pictures of panels with moss built up on their bottom edge, although I haven’t seen anything like that here in South Australia. If moss is starting to cover solar cells I definitely recommend cleaning that off or having it cleaned off.

  35. I can confirm that I have seen moss AND Lichen on the same west-facing panels here in Adelaide.
    Salisbury North to be exact. In 2015 my wife and I moved to Adelaide from FNQ and initially housesat our way around Adelaide as a means of finding a suitable suburb to buy in.
    This house at Salisbury North had panels in place for just a few years when I arrived.
    The house owner fed the birds every day and as a result the top knot pigeon, dove and sparrow populations hung around on his and neighbouring rooves as feeding time drew near.
    The mess was appalling – I could see from the ground that the panels had streaks of droppings on them. It was only when I got on the roof to clean them, that I saw the moss and lichen.
    A soft broom, detergent, elbow grease and a good hose pressure soon cleaned them up and the difference in readings was amazing.

  36. George Schueler says

    Before rain maximum output on a 20 panel E-W facing system was 3800W mid day.
    After 50 mm rain output rose to 5100W mid day.
    No rain for 4 months and little for previous 5 months.
    washing wit rain seems to help.

    • If you hadn’t had virtually any rain for 9 months then there would have been a layer of dust built up on the panels which would have a similar effect I’d imagine as an overcast day if the dust was impeding the rays getting through the glass to the solar film. The rain would have cleared the worst of it but I’d almost guarantee that it didn’t wash it all off just as rain doesn’t wash all of the film of dust and dirt from your car.

      If your numbers are right then 1300 kw/h odd a day multiplied by many months is money lost ! If climate change continues to make Australia drier for extended periods then washing panels in cases such as yours will definitely be cost effective.

      • Daniel Debreceny says

        1300 kWh per day from 5100W panels? I guess he must have a VERY sunny location … eg; the sunny side of Mercury …

        @George .. you’ll need to clarify your situation. I’m curious how your panels managed to get so filthy?

        Lets all get our units correct, before applying mathematics and discovering amazing payback ….

        Let’s do the maths:
        1300W difference (1.3kW) x 5hrs/day (full production average over entire year) x 365 days = 2,372,500 Wh / year, or better presented as 2,372.5kWh per year.

        Using the highest FIT available (AGL / Origin = 20c/kWh) equates to: $474.5 per year.
        If you are on a typical FIT, (12.5c), then it equates to:$296.56 per year.

        It’s basically a wash if you have double story house.
        Single story is probably worth doing it yourself, with a Garden Hose.

        • Richard V Anthony says

          Tap water leaves minerals on the glass (unless you can hand dry them) and leaves a rough surface that collects dirt faster going forward. Whenever I see or hear someone suggest spraying them with a hose I know they don’t know much about this subject matter. The issue here is heat, they don’t like it. Dirty panels run approximately 12* hotter than clean ones and for every degree over 107* they lose 1.5%. Panels here in Arizona can reach the 130’s and up, do the math. Some of the argument over cleaning vs no cleaning does depend on where you are and the climate there.

  37. This is quite an interesting area for discussion, unfortunately there have been personal attacks etc which doesn’t help anyone. Every one of us has an opinion or a belief, some based on fact (even that can be questionable) or what suits them best. If cleaning them ( professional or DIY) makes you feel better go ahead and do it.

    I clean my 18 panels yearly by using a ladder at ground level with a hose and a soft brush placed into one of those long extendable handles that you clean a swimming pool with, it works a treat. It cost me $28.00 at the local Big W .The amount of grime that comes off is quite noticeable.

    I use a ladder instead of getting on the roof as I have lost confidence getting up there now due to balance probs. I hang onto the gutter for extra stability which is reassuring.

    I feel better for doing it, even if I only get a small increase in performance, that’s a money in my pocket. I get amazing performance out of mine, saving me about $1,100.00 per year at 15 cents per Kwh feed in tariff.

    In 2016 I had 5194 kWh fed back into the grid and 5495 kWh in 2017. My annual bills were $435.87 for 2016 and $174.25 for 2017. I believe getting a low bill isn’t just about cleaning your panels, it has to be viewed as a part of a bigger picture.

    Installation of LED globes, installing awnings over windows to cut down on heat thereby reducing cooling costs, partially closing blinds, turning off unnecessary lighting or electrical equipment, only filling your kettle/jug with required amount of water for your coffee etc rather than boiling a litre of water for only a cup full.

    All these things add up in the long run, it just requires you to look at what you do during the day and work out how to improve efficiency.

    I even installed a temperature controller on my instantaneous gas water heater. I set it at 38 degrees Celsius to have a shower and just turn the hot tap on and jump in. Why have your water temperature set at 50 degrees and then cool it down with cold water? Seems a waste of energy to me. Also, if you are having a shower and someone turns on the cold water elsewhere in the house while you are in the shower your temperature does not vary at all. It is just commonsense and a little bit of thought involved.

    There are many many ideas that increase efficiency around the home that will complement cleaning (or not) your solar panels….it just takes a bit of consideration…kindest regards to you all…Michael

  38. Richard Anthony says

    How much you will gain by cleaning panels is debatable and varies according to a variety of factors; type/brand of panels, direction, dirt load, (tree pollen, bird droppings, etc.). We see gains by our customers from 10% to in the area of 20%. Heat is the enemy of solar and light is their friend. The dirtier they are the hotter they are and the less light they let in so it’s just common sense that clean is cooler and more productive. The question is so much is why should you clean them it’s more about how. If you’re using tap water and can’t dry them before the air does you’re creating a longer term problem. The minerals dry on the glass and make it rough, more able to hold dirt going forward. Imagine spraying your car with a hose and letting it dry in the sun. The way we do it is we use only deionized water; zero mineral content and no chemicals added. They dry spotless and as clean as that first day, actually cleaner because newly installed systems often aren’t that clean, fingerprints etc. The question that should really be asked is “why wouldn’t you clean them”? It’s the only cleaning you can do that will pay for itself and it will extend the lifetime of the overall system, gets the dirt out of the frames too.

    • Daniel Debreceny says

      How much energy/resources are consumed de-ionising each litre of water?
      How much water is used to wash each panel?

      Which process is used to de-ionise the water, and what’s the embedded energy of the products to de-ionise the water?

  39. Richard V Anthony says

    Sounds like you are going to oppose cleaning them no matter what. The de-ionizing is accomplished by passing R.O. water through a mixed bed resin tank, .5 cu. ft. and by feeding it TDS water of under 10 it will deionize about 3,000 gallons. That resin costs about $125 to replace. Embedded energy? After exposure to the elements the deionized water becomes inert so I don’t know what you’re referring to. On most jobs the usage is about 1 gallon per panel.

  40. Don Bollinger says

    Interesting Site. I live in Washington state, near the coast, not the greatest solar place but ok. I get pine pollen on my panels every April-May. It does not wash off. so I clean the panels with a ladder roped to the house and a brush with a 24 ft handle.

    Regarding solar improvement, I have micro investers, and std practice is to slightly undersize them. They flat line out for 2 hours on sunny days, so it would be hard to measure the “iimprovement.

  41. Hi Ronald,
    I would love to hear your view on the latest release by Energy Matters about cleaning of panels,
    They are saying you will lose up to 30% productivity a year from dust if they are not cleaned.
    I find this very hard to believe, as I monitor hundreds of solar’s and I do not see anything even close to 30% loss due to dust.

    • Ronald Brakels says

      Looking at the white paper they got the information from, I see it is for ground mounted solar modules in semi-arid conditions. So, yes, it’s 100% true ground mounted solar panels out the back of Burke can get covered in a thick layer of dust. But it’s not something most Australian homeowners have to worry about.

      • But you have to admit that it is still an issue Ronald and measurable like all the other stats you are happy to go to a lot of trouble to calculate and put up here.

        If we are going to worry about the differences between one panel to another and one inverter to another then surely we should be wanting the best bang from our buck from our investment and worrying about the cleanliness and efficiency of our panels from one clean (or not) to another !

        • If you read any scientific study on cleaning panels you will find that, although there is a measurable increase in output after cleaning, in most cases (read Australian conditions) the increase is not enough to justify the cost of having them cleaned or the time spent on doing them yourself.

        • Des Scahill says

          My simplistic cleaning method is to stand on the ground and direct a hose spray at the top of the panels at one end of the string, and work downwards and across, with the run-off going to the roof-guttering down-pipes.

          Repeat that process a few times – you usually need to allow a few minutes or so for the first lots of spray to soak through dust and bird poo etc before it gets flushed off.

          If your panels haven’t been washed off for quite while, or not at all, it may take longer the first time around,

          I seem to get about a 3%+ increase in output at times (depends on the level of dust), usually only do this about every 2 or 3 months. Thats not much, but its easy enough to do, doesn’t take much time, so why not. All you are really doing in effect is replicating the effects of a rainfall on the panels, so its quite safe. Helps clear your gutters out as well.

          Here in SQ, due to the absence of rain for quite a long period, the build-up of dust over a couple of months is quite noticeable, and as well, the bushfires have probably added their contribution to atmosphere particulates too

          • Richard Anthony says

            You get 3% because they’re still not clean. Have you ever tried washing your vehicle or the windows on your house that way?

          • Ronald Brakels says

            Err… yeah.

            Higher wages mean our standards are a bit lower here. My bank manager irons her own blouses.

  42. You are so funny, Ronald Brakels!

  43. Hi guys, just wondering if my comment has passed the moderation phase yet, sent in on the 19/1/2020

    • Looks like it got lost, Darrell. Maybe they’re on hols!

      • Darrell Veal says

        Hi Jeannie,
        Thanks for the reply, I thought I would wait a few weeks for them maybe to get back from hols, or reply to say they had found the lost reply, but alas it is not to be. Sadly this is the third time this has occurred, bit funny that. Just hope this doesn’t validate more to the point of what I was trying to say to Richard V Anthony, although now he will never know. Maybe one day they will come across the “lost” speak your mind box.

  44. Jim Phillips says


  45. Paul Croskrey says

    Where we live in California, with all the agriculture going on we see 30% to 100% loss in production in as less then 3 months after the rainy season. Depends on the location.

    Our firm is hired to wash these panels sometimes 6 times a year.
    Sure if you got 12 solar panels and your in a arid location it might not be worth hiring a panel washer but would be worth it to do it yourself.
    Depends on how much they charge.
    However if you got hundreds or thousands of panels the cost to keep em clean always provide a decent return on that investment. Better to have a return on your investment then provide a return to the utilities because you THINK you don’t need to keep your solar panels clean.
    Being a company who overall cleans over 2 million panels a year, the multitude of companies who repeatedly hire us every year will tell you it pays to clean the solar panels.

  46. We live in Santa Barbara, CA where it really only rains heavily enough to wash the panels for 3-4 months in the winter. April showers are rare.

    We also live near the ocean, so the daily fog and dampness are just part of most nights and mornings all throughout the year. As a result, the breeze and the dust of maintenance gardeners blowing stuff around, or just the natural flow of pollen and sometimes ash from forest fires are what usually land and stick on the 44 some odd panels (half are 13 years old, the other half, just 3) we have at an angle on our roof.

    We even have moss that will grow under them and sometimes (seemingly) on them in spite of the summer sun. We’ve been told we’re in an ideal place for solar panels too because we have a lot of sunshine, but it rarely gets uncomfortably hot. They produce well as long as there is light.

    Given this setting, it seems that cleaning them once a year in August (as we just did last week) can really help. We had them professionally cleaned and will monitor the improved production, but it seems noticeably higher, at least 5% (according to the Tesla app monitoring our PowerWalls and entire setup), possibly 7-8%. The weather, until the rains come again in Dec/January, should be fairly dry and sunny with the least amount of fog and overcast days till then. For us, it seems the $125 I negotiated for to have them professionally cleaned (they wanted $180-$220), was worth it if we care about getting the most out of our panels.

    Sure, the increase in production my not equal the cost of having them cleaned, but we wash our cars too and that does nothing to their performance either.

    Sometimes it’s just nice to know there is nothing between them and the sun.

    • Very well said Mick. You summed up the argument perfectly.

      • Well, I hope I did. They sure look beautiful right now. Paired with the Tesla PowerWalls, we’re nearly off the grid. We’re going to get a 3rd and that should get us all the way through the wee hours of the morning until the sun starts producing again.

        We’ll still have to borrow from the grid during the rare rainy or completely overcast days of the year, but the power company rips you off so badly when you give the extra power to them, that we just wanted to capture all we could and use it ourselves.

        It will be interesting to watch production over the next week or so and see how much higher it is (or not).

        • That will be a good feeling to be nearly independent from the power company Mick.

          In winter I too get moss growing on mine on the bottom parts of each panel on the small lip between the glass and the frame (most of the water flows over the bottom edge and onto the roof after it runs down the glass but some probably sits there long enough to produce the right moss conditions especially in winter. Although I am no botanist I suspect that the moss probably also gets some nutrients from the grime that gets washed down the panels and sits in the same place after some rain. I have a TV antenna that birds like to sit on over the top of some of the panels so I used to get a steady build up of bird poop that bakes on and clearly doesn’t all get washed away with the rain. I have stopped the birds perching with a plastic “bird scarer” falcon that I attached to the aerial with stainless steel zip ties. That just leaves the clearly visible film of dirt on the panels that I clean off myself every twelve months or so.

          Whilst I am still young enough to get up and the work myself it costs me little except some time – I get a beautiful water view from the roof whilst I’m up there and the inner satisfaction of knowing they are producing as much power as possible in their newly cleaned condition !

          • Yeah, if I could clean my own, I would, but I think my roof days are mostly done as the medication I have to be on makes me a little dizzy.

            I haven’t seen the big spike in solar production I thought I might be seeing during the first few days, but even if it’s marginal, I think it’s worth cleaning them in the middle of the very dry and dusty summers here.

  47. What about the build up of grime and bacteria causing lichen growth?

    Knowing the solar industry there is also the benefit of having a performance/quality check to ensure system is installed correctly and safely. So having a team trained in solar, out cleaning panels, could be a great way to ensure consumers are getting what they paid for.

    Obviously my second point is not directly related to cleaning I believe it’s something worth considering?

    • Keeping a reasonable record of your output is a good way of keeping track of the performance of your system. Sudden drops in output (allowing for cloudy days) compared to normal for that time of year is a good indicator of a fault in the system.

      You can scrape lichen off with a plastic scraper. No water needed which makes your time on the roof safer than when it is wet.

      There is plenty of evidence out there to demonstrate that cleaning for most panels doesn’t justify the time or cost. Unless there is solid blocking from leaves, bird (or bat) shit or a thick film of dirt, rain does the job perfectly well.

      Don’t be sold the promise of huge increases in output from someone who wants to clean a thin film of dust off your panels.

  48. In Brisbane we get bats. Bat poo dries nearly instantly to a consistency of concrete hardened in a blast furnace. Bats hang upside down, which makes taking a dump fairly unpleasant presumably. They get around this by releasing their load on takeoff, which in our case is over the house and more particularly over the solar panels. I clean the panels every three months or so, and get an immediate performance improvement in the next bill of about 10%, sometimes more.

  49. I may have bird poo on one of the panels, as might be underperforming a little, as these crazy immigrant Indian Myna birds are a pest!! It’s really easy to get up on my roof to clean the panels.

    I know how to turn the PV Isolator switch down near the meter box but do I turn off the Isolators on the roof too, at the end of the panels?

    The panels are on about a 9% tilt.

    I was going to clean the affected one or ones early morning or late arvo, when there is less charge in them?

    Any recommendations? cheers Mick

    • Daryl Wilkinson says

      Warm water and a cloth,, don’t use chemicals in the water, it can tarnish the glass.

    • Ronald Brakels says

      Well, as the article says, I don’t recommend going up a ladder and cleaning them. I’d say either wait for rain and see if that helps or use a hose to rain water down on them when they’re not hot. Or if it’s bugging you and you have the money, you can pay someone to clean them and let them risk their neck.

      Some people will say I’m biased because gravity exerts much more force on me than the average person. But that doesn’t worry me. I’m big enough to take those jibes.

  50. 100% about, bigger system is cheaper then cleaning efforts.
    but, some places in USA where is under NET metering, over size is not allowed. It is a problem.

    • I’m a Photovoltaic / Solar Thermal Technician. You are correct about some places in USA hence Los Angeles County. but certain parts of Riverside County you can. I sure did my brothers house 9,280 Watts total. will be adding some battery backup too, now that he has the money to buy battery. He’s thinking Tesla Powerwall since he works for Tesla, I want to use Enphase battery since I want to try something new.

  51. Hi

    I live in Sydney and had some panels for about 7 years, in the last few years a lot of Lichen started growing on them. Is this a common problem? I’ve noticed it with some neighbours but other neighbours panels seem fine.

    I get a lot of morning shade from a big gum tree. I wonder if the morning dew isn’t evaporated b/c of the shade and maybe this contributes to the lichen by providing moisture.

    Any advice on prevention and cleaning of lichen?
    Any brand of panels that are more lichen resistant?


    • Warren Harvey says

      Lichen is spread via spores so this is perhaps why only your panels are affected and your neighbours not. Being in the shade of trees probably didn’t help as well, although I had some lichen attach itself to my solar panels in full sunlight and happily grew there before I noticed it. I also had lichen grow on my solar hot water panels as well under full sun conditions without trees being in the near vicinity, so the damn stuff is very robust under nearly all conditions I think. I believe you could put it down to bad luck that you have it grow on your panels and other don’t have the problem – yet! As for getting rid of it that’s easy, but you will need access to the panels…..which is why I anticipated this and installed mine, not on the house roof, but on a purpose built frame built on ground level and the panels up from there. Wait until the early morning when the dew is nice and heavy, then scrub the stuff with a stiff broom and a wash off with a hose. The lichen tends to release itself really easy when affected by dew overnight and takes no effort at all to remove. Don’t know anything about different species or how it might be prevented from affecting panels, and I doubt there’s a brand of panel which is resistant to lichen in general. Jpoe this helps.

    • Scrape it off with a plastic scraper, comes off fairly easily.

    • Ronald Brakels says

      It’s likely the morning shade is what allows the lichen to grow. Here, Adelaide roofs are mostly lichen free, but where there’s enough shade and moisture it can grow. Some panel warranties specifically state they can only be cleaned with a soft cloth, while others aren’t so strict and allow “mild” detergents. There are chemicals that can remove lichen but you would need to check with the manufacturer if they can be used and, if so, in what concentration. Unfortunately, it’s likely they’ll just say “use a soft cloth”. That will get them clean eventually, but it’s awfully hard on the elbows and I don’t recommend going up on roofs anyway. I normally recommend getting them professionally cleaned to be on the safe side.

  52. LICHEN
    What about cleaning lichen off?
    Seems to me one should get the lichen off… or it will just keep growing…

    • Ronald Brakels says

      Lichen can’t survive on most rooftop solar installations, but in a location where it does grow then cleaning may be necessary to keep it off. How often cleaning will be needed will depend on the situation.

    • Warren Harvey says

      I would definitely clean any lichen off.

      We live in Qld and our solar panels developed lichen (over about 15 years) on the face of the panels to varying degrees and it took quite bit of effort to get them clean using a very stiff bristle brush and plenty of water. They are situated in full sun with no trees in the vicinity to provide shading.

      I’ve also seen panels on two other premises where a lot of the panels produced very little power due to the covering of lichen all over them. Once cleaned off they began functioning quite well again.

      We also had a solar hot water system on the roof of our house which grew lichen on the collectors very well, so the stuff appears to be extremely resilient when it comes to these types of structures.

      Being out in the full Qld sun doesn’t seem to worry lichen one bit, although the panels do suffer themselves from the hot temperatures during the Qld summer – as can be attested by the lack of power efficiency as the day progresses and temperatures climbs.

  53. Scott Meloni says

    Hi Ronald,
    Interested in any updates related to this Blog. Considering the up coming electricity price rise. If you are working on cleaning increasing performance by 5-10% even, and the electricity price rise estimated to be 20-30% what would you calculate now being the benefit of cleaning your Solar? I myself as Paul mentioned am a Solar Cleaner and have found a constant performance gain of between 10-20% over time, I am located in an industry town being Gladstone QLD so there is way more contaminants in the atmosphere here than just dust.
    Thanks, Look forward to your response, or maybe even an updated Blog on the subject 🙂

    • Ronald Brakels says

      Unless the panels are clearly grimy, cleaning them will only likely improve output by a couple of percent. So even with increased electricity prices, it’s not likely to pay for itself. Especially with Gladstone rain regularly sluicing down and hopefully keeping your panels clean. But it’s still possible for panels where you are to get dirty enough for cleaning to be worthwhile, whether it’s due to pollutants or birds, so it will depend on specific circumstances. Fortunately, modern technology can make it easier to tell if your panels need cleaning. Just grab a kid and get them to illegally fly their drone over your roof so you can see if a clean looks likely to be worthwhile.

  54. Nathan holt says

    I think half of it just depends on your local conditions.
    I get while less then i used too a LOT of dust in the air from a nearby quarry.

    For when i get the new system up i will probably mostly just occasionally aim a hose up to sprinkle down like rain mostly to make up for how unpredictable our rain is
    “my first thought when it rains is to ask if theres a cyclone off the coast because half the time there is”
    Admittedly it has been raining more often recently.

    Though i will probably get someone to clean them if either i see something that doesn’t just wash off or every 5-10 years adjusting to how they deal with it.

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