#1 cleantech news, reviews, & analysis site in the world. Subscribe today. The future is now.

Clean Power

Published on April 12th, 2013 | by Ronald Brakels


How To Maintain And Clean Rooftop Solar? Don’t!

April 12th, 2013 by  

As you can see, my first attempt at solar cleaning fell about 93 million miles short. Image credit: Me

As you can see, my first attempt at ‘solar cleaning’ fell about 93 million miles short.
Image Credit: Me

One question I’m continuously being asked is, “Ronald, what’s the best way to clean and maintain rooftop solar?” As a result, I’ve resolved to never again teach my parrot to say stupid sentences. But if you were to ask me this question, my answer would be that the best way to clean and maintain your solar power system is not to. This is because, unless your situation is unusual, it is a waste of time, effort, and quite possibly money. Now don’t get me wrong, if cleaning and maintaining stuff makes you feel good inside, or even externally, don’t let me come between you and a source of happiness. But most people will be better off if they skip it because it’s simply not worthwhile.

When you first get rooftop solar, your installer may offer to come around and perform a one-year service in return for a potentially substantial fee. I can’t recommend this lowly enough. After all, you did get a 25-year warranty for the solar panels and a 10-year warranty for the inverter, didn’t you? And you did make sure it included onsite repair or replacement so you won’t have to mail your solar panels to China? And surely you got one backed by a third party so that if the installation company disappears your warranty won’t? And even if you didn’t get all that, you at least got a long-term, onsite warranty that you’re confident will be honoured if need be, right? Well, if you got that and if anything goes wrong they’ll have to come and fix it for free anyway, so unless it is an unavoidable condition of your warranty, it makes no sense to pay for a one-year maintenance check. There’s just no point in blowing a load of cash on a maintenance man. Trust me, I’ve had a lot of maintenance men in my time and very few of them have been worth it. I heartily recommend keeping your cash in your pants.

As for performing maintenance yourself, just exactly what would you be planning to do? Rooftop solar has no moving parts and the inverter is just a box that sits there, inverting away like nobody’s business, and is full of technical stuff like wires. Do you have any idea what you could possibly do to it to make the system work better rather than worse? I certainly don’t. Unless you really know what you are doing, I strongly suggest you leave it alone. About the only thing the average person could do is keep the cobwebs off it. Just watch out for redback spiders. I was bitten by a redback spider once and it was the worst experience of my life. No wait, sorry, actually it was the worst experience of her life. If any arachnids are reading this, be warned – don’t mess with a primate that’s a million times bigger than you or you’ll end up taking a trip to squish city.

Another thing solar panel installers may offer to do is come around and clean your solar panels, again for a fee. I don’t get this at all. Without special circumstances, there is no point in getting your solar panels cleaned. That’s what rain is for. Basically, they are self cleaning. Sure, there are exceptions, if you’ve been hit by a dust storm you may want to hose off the panels, and if, for some reason, your rooftop solar is underneath a tree that has recently been taken over by a colony of fruit bats – well, you’ll probably want to move house because I can tell you now you’re in for a crappy time. But for the most part, owners of rooftop solar report very little difference in performance after having their panels cleaned. Even if you’re willing to do it yourself, it’s generally not worth the effort and almost certainly not worth the risk of mucking about on the roof. If you want increased output from your solar panels, rather than clean them, it’s much easier and more cost effective to simply install a slightly larger system from the beginning, so if you lose a little bit of output from dust and grime it’s not a problem.

We know that properly made solar panels have no trouble lasting over 40 years, and solar inverters can easily function for far more than 10 years, so provided you took the care to purchase a decent quality system, you should be able to sit back and do absolutely nothing for over a decade while your solar panels silently work at turning sunlight into power for you, letting you rake in the savings on your electricity bills without any need to blow it on maintenance or cleaning fees. You can instead take your money and blow it in a totally different way.

Tags: , , , , , ,

About the Author

lives in Adelaide, South Australia. Now that his secret identity has been revealed he is free to admit he first became interested in renewable energy after environmental mismanagement destroyed his home planet of Krypton. He is keenly interested in solar energy and at completely random intervals will start talking to himself about, "The vast power of earth's yellow sun."

  • Sonia Cannon

    Most things maintained last longer than those that aren’t. A little care and maintenance of a large or small investment generally means you reap the rewards of the product, simple as that. On the argument of your warranty : most warranties become null avoid if proper maintenance is not adhered to. The old saying goes ” laziness never pays off!” There are many parts of Australia that don’t get much rain and when it does rain it rains dirt! The large portion of Australians living along the coast would also know that rinsing salt particles off their solar would have to be beneficial long term. There is more to think about over the life of your system than 1 test done days apart on cleaning or not cleaning.

  • Accent

    We live in northern Sydney and our outdoor furniture and cars are regularly covered by a black, sooty film. Not sure if it is sooty mould from the abundant gum trees, motor-vehicle pollution or aircraft fuel dumped as they fly into Sydney, but I assume it must also affect our solar panels. I hesitate to go up on our high, steep roof to have a look though. The panels have been up about 8 years and never been cleaned. Any thoughts?

    • Bob_Wallace

      Rig up a brush with a long handle made of PVC pipe. You may need to use 1″ (or metric equiv). Spray on some water, use the brush, spray again.

      If the sooty film on your cars, etc. isn’t easy to get off you might want to try a hose end sprayer to spray some detergent on your panels before scrubbing.

      You should be able to clean them from the ground. (I clean my skylights that way. My panels are ground mounted.)

      • Accent

        Thanks Bob. I’ll give it a shot from above. I can climb the back of the building and lean over the ridge. Not being the youngest of folk cleaning from this angle will be a challenge. Hosing from the front would be very tricky.

        • Bob_Wallace

          From the top should be easier. Your pole wouldn’t need to be as rigid. 3/4″ PVC should work well.

          I’d suggest looking at the sponge mop refills at the grocery/hardware and finding one you could wire to the end of your pole. Get something that would hold a good amount of soapy water. My sponge mop uses a head that has a metal backing which already has holes in it. A single hole through the end of the pole would let you wire it all together so it wouldn’t slip off.

          If you can get it where you are Dawn dishwashing liquid does an excellent job on greasy/oily stuff. It’s the go-to for diesel spills.

          And put a squirt nozzle on your hose. It should be a fairly easy job which wouldn’t take long. I wash my panels down with a sponge mop in no more than ten minutes.

  • confused

    Has anyone had a dramatic decrease in in their credits .we dropped from $950 a quarter to owing $23 , we’re signed up with originenergy, when I enquired about it , l was told the storms might of damaged panels has this happened to anyone else

  • SolarSaver

    Im sorry ronald I 100% disagree with you. Fronius inverters have intake fans and air outlet filters that need to be checked, and cleared of any dust and debris. The inserter manual even says it. And also is a proven fact with many years of study that dirt build up on panels causes 10-25% loss of efficiency on solar panels and no amount of warranties will fix that.
    Also leasing agencies and solar city and other large companies monitor your system but they dont and will not put any concerted effort out to come and clean your panels the money it costs to pay a laborer to do that would be better spent installing and making a larger profit….. I have 10 clients that are leased the systems are 10 yrs old and not a single one of there leasing companies has come out and maintained them like they said……proven fact….

    • DB Denver

      I spent my time reading this article hoping to get some real professional information. All I GOT WAS A ONE MAN OPION WITH OUT ANY SICIENCETIF DATA TO BACK UP ANYTHING BEING SAID.
      Please learn how to back up your statements with facts or keep them to your self.

  • JHoughton1

    This is the worst nonsense I’ve ever seen! In places (like here in So. Cal.) where solar pays off in spades, there is very little rain and lots of dust. A few days’ worth of dust (turned into muck by morning dew) is enough to reduce output of my 42 panels by ten percent. The idea that they don’t need to be clean is beyond stupid! Hosing them off regularly from the ground helps, but over time they need to be cleaned with a brush on a pole.
    Naturally, the people who sold me the panels didn’t mention this problem, but luckily I have a one-story house. I really feel for homeowners who’ve put a ton of money into arrays that are inaccessible for cleaning. They are not getting their money’s worth. I have no idea who this Ronald is, but he is handing out extremely bad advice to anyone who lives in the sunny (solar-friendly) part of the world.

  • MyEnergyMan

    I can tell you its important to clean and maintain your panels, As an owner of a solar panel cleaning business called Solar Maid at http://www.mysolarmaid.com
    I see all types of situations in my many years of doing this work I have never seen a job that did not need cleaning except new installations less than 6 months old. You should according to the manufacturers of solar panels inspect and clean them twice a year to get maximum efficiency and long term use from your system.
    I got a call from a Solar panel user in San Jose telling me their panels are not producing power like they used to two years ago when they were first installed. They thought that they did not need cleaning, The panels were producing 80% of what they should have been. Once professionally inspected and cleaned they were back to 100% This person was experiencing a 20% loss due to grime and dirt. Try not washing your car window for a year or two and see if you can see out the window. Its the same with solar panels… dirty panels equalls less production.
    Our prices are fair and the work is professional. why would you invest thousands of dollars in panels and not clean or maintain them. You know roofs have warrantees as well that does not mean a 20 year roof can be abused and still keep your head dry when it rains what do you do when leaves are on it? you clean off your roof…same with solar panels when they are dirty.

    Solar panel leasing companies hire our company to clean their system why not you?

  • Steve Williams

    If solar panels do not need to be cleaned in you opinion, how can you explain these figures from respected sources? http://www.solar-panel-cleaners.com/why-clean-solar-panels.php

    • Bob_Wallace

      Well, we can start with the fact that your site is not truthful. It reports that Google found that it needed to clean panels mounted flat. It does not report that panels mounted on a slope did not require cleaning.

      “Ever since we assembled a 1.6 MW solar panel installation at our headquarters in Mountain View in 2007, we’ve been wondering, “Does cleaning the solar panels make them more effective?” We thought it might, but we needed to be sure. So we analyzed the mountains of data that we collect about the energy that these panels produce — after rain, after cleaning and at different times of the year.

      We have two different sets of solar panels on our campus — completely flat ones installed on carports, and rooftop ones that are tilted.

      Since the carport solar panels have no tilt, rain doesn’t do a good job of rinsing off the dirt they collect. (Also, our carports are situated across from a sand field, which doesn’t help the situation.) We cleaned these panels for the first time after they had been in operation for 15 months, and their energy output doubled overnight. When we cleaned them again eight months later, their output instantly increased by 36 percent. In fact, we found that cleaning these panels is the #1 way to maximize the energy they produce. As a result, we’ve added the carport solar panels to our spring cleaning checklist.

      The rooftop solar panels are a different story. 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.”


      Then there’s this –

      “PV module Degradation: One partnering PV module manufacturer recently retested PV modules which had been in service in Tucson for 28 months to test for dirt and time related output degradation. Modules were tested first without cleaning and then after cleaning.

      Results indicated soiling effect was less than 1% output degradation from modules which had not been cleaned in two years and overall time related degradation of clean modules much less than that expected. 9,000 of these modules are used in the SGS solar system. SGS modules have historically been cleaner than Tucson located modules due to no oily deposits and the ability of snow to very effectively remove solid deposits like bird droppings.”


      Now, there are some other claims on your site that claim cleaning is needed but they aren’t linked and after the one incident of dishonest I’m tempted to dismiss the entire site.

      After all, it is a site set up to move money from panel owners to the site owner’s pocket.

      And the World Academy of Science and Technology????

      You gotta bring better stuff than that Steve. Your site is a fail.

      • MyEnergyMan

        The results on tilted panels in Mountain View is different than in Livermore or the Valley like where I live in Oakdale. I have seen a 40% drop in production after the farmers shack the walnut and Almond trees to get the nuts. In Stockton they got duct from the peat bogs. Just three months in that area and you can have a 15% to 20% drop in production. Its not me saying this stuff its our customers I am only repeating what they tell me. To say just because in Mountain View tilted panels are cleaned by rain sufficiently to not be a issue could be true for Mountain View but not in other areas that are not all blacktop and concrete like in the central valley or even lower San Jose.

        Last month our company cleaned over 30,000 panels….we know from experience. .

        • Bob_Wallace

          I lived on a sailboat in the Delta for a while. Yes, a peat storm is a unique event. Peat mixed with rain is a sticky mess that blows sideways.

          In very limited unique situations panels will need a cleaning. I used to have to clean mine off during blackberry season. For some reason birds thought they made excellent loos.

          You might have cleaned 30,000 panels. I’d bet a lot didn’t need cleaning.

          (I took down your ad. If you’d like to contact Zach about purchasing some ad space….)

          • MyEnergyMan

            Thanks, I know what you’re saying about panels that do not need cleaning…we always tell the customer when we notice that cleaning will only make them look nice and not increase production and believe it or not about 10% of our customers want a clean look and are not really interested in the efficiencies…its because they are right in their face and they have huge incomes , these people clean their windows twice a month you can imagine what they do when they see dust on their panels. Over 90% of every system we clean we can show increases of 5% to 38% in increases.of power production.
            Thats what our customers tell us.
            Facts are facts people tell me that when we do our work they have more power production and they call us to do the job every six months,. Companies like Sun Run, Acro Electric, Solar Universe so many too many to name use our services. We are the only company with international exposure and we have an A+ rating with the BBB.

            I would appreciate buying some advertising space and I would like my posts to be seen if I do. Its possible I can get a few jobs each month from your site. I have upto 20% of my fees go to marketing so if your service is effective we are game.

            I own the local Solar Maid, I cover Central California, it is a pleasure communicating with you regarding this issue.
            Lets do business and help people save the planet


            Paul Croskrey

          • Bob_Wallace

            Bottom left of the page. “Contact us”.

            You can talk to Zach about purchasing ad space on the page but you can’t advertise in the comment section. Any more comments bearing company information will be taken down.

            If you’ve got information about solar or clean tech in general, chime in. Just leave the ad stuff out.

  • codeslubber

    Wow this is so stupid, my head hurt by the second paragraph. Um, here in Los Angeles, we can easily go 8 to 9 months without rain. And the crap on the panels greatly decreases the power they generate. Which, after all, is their purpose.

    But thanks!!

    • Bob_Wallace

      ” One partnering PV module manufacturer recently retested PV modules which had been in service in Tucson for 28 months to test for dirt and time related output degradation. Modules were tested first without cleaning and then after cleaning.

      Results indicated soiling effect was less than 1% output degradation from modules which had not been cleaned in two years and overall time related degradation of clean modules much less than that expected. 9,000 of these modules are used in the SGS solar system. SGS modules have historically been cleaner than Tucson located modules due to no oily deposits and the ability of snow to very effectively remove solid deposits like bird droppings.””


  • Ronald Brakels

    Just in case someone wants some numbers on my assertion that it’s generally not worthwhile to clean your solar panels, let’s say you’re an Australian and you have a job casually stacking groceries on shelves at the local supermarket and so value your time at the same rate you earn money, which is roughly $21 dollars an hour. Dirt reduces the output of your average sized three kilowatt solar power system by 2% and by spending one hour a year cleaning you reduce that loss down to 1%. This means that, in a sunny part of Australia, one hour’s effort will result in you producing about 50 kilowatt-hours more a year than you would otherwise. Assuming you would have used all that electricity yourself, which is unlikely but possible, then at the average Australian electricity price of around 28 cents you would have saved yourself $14, which is well below the value of your time. And then there is the risk of falling off or through the roof while cleaning your solar panels which should also be factored in, but this is difficult to do as the total risk depends on factors such as weight, clumsiness and skull thickness.

    And because some people’s skulls are particularly thick, I will mention that I am speaking generally. If a dust storm deposits a layer of the Great Victoria Desert on your solar panels, or they get covered in poo, it might be a good idea to clean them.

  • Otis11

    Just one comment – the fastest way to kill and inverter is by overheating it, which mainly happens after a few years of gathering dust. So if you’re semi-handy with a screw driver, I’d recommend getting some rubber gloves, cracking it open, and blowing it out with a can of compressed air. Make sure to turn it off, that the gloves are rubber and that you use compressed air, not a vacuum. Also, let it sit for an hour in the off position before opening it up as the capacitors need to discharge.

    With that, the inverter should last indefinitely because just about the only thing that can go bad is the fan (which is easily replaceable) or a capacitor (which is moderately replaceable for someone with a solder gun. Also, the reason you don’t use a vacuum – vacuums can produce large amounts of static electricity that can then arc and kill electronics. Never use a vacuum to clean any electronic device.

  • Great article. Makes me feel better about not touching my panels. I am leasing my panels from Sungevity. $0 downpayment. Low monthly lease. You can get free quote at sungevity.com and use referral code 94755 for $750 discount.

  • jonesey jonesey

    I live in a part of the Pacific Northwest where the average rainfall between July 1 and October 1 is about one inch. My panels get pretty dirty just from dust and pollen that flies around and lands on them. I wouldn’t be surprised if my once-yearly midsummer cleaning improves their performance (I suppose I could pick two very sunny days and do a before/after comparison, but that’s a pretty small sample size).

    It also gives me an excuse to go up and check on the condition of my roof and clean off the skylights, so there’s really no marginal time cost for me to hose down the panels.

    I’m with you on this, though: I’m certainly not going to pay someone to do it as long as I am healthy and able-bodied, however.

    • Bob_Wallace

      Here’s an interesting piece that Google put up about their panels mounted just south of San Francisco. In short, their flat-mounted panels (top of carports) did benefit from washing. Their slope-mounted panels didn’t need it.


      There was a study in Arizona, close to Tuscon IIRC, that didn’t clean a set of test panels for over a year. They did pre- and post-cleaning measurements and found that cleaning only increased performance about 1%.

      (I need to find that link. If anyone else can find it, would be helpful.)

      • Bob_Wallace

        Found it. A lot over one year…

        “PV module Degradation: One partnering PV module manufacturer recently retested PV modules which had been in service in Tucson for 28 months to test for dirt and time related output degradation. Modules were tested first without cleaning and then after cleaning.

        Results indicated soiling effect was less than 1% output degradation from modules which had not been cleaned in two years and overall time related degradation of clean modules much less than that expected. 9,000 of these modules are used in the SGS solar system. SGS modules have historically been cleaner than Tucson located modules due to no oily deposits and the ability of snow to very effectively remove solid deposits like bird droppings.”


        • JHoughton1

          I don’t know who ran that test, but you’re welcome to come to my house and watch me add up to ten percent performance to my panels by cleaning them after as little as a week gathering dust in Los Angeles.

          • Bob_Wallace

            Well, you could click on the link and find out.

            As the article says, there will be exceptions. Perhaps you’ve chosen to live in a very dirty place.

          • JHoughton1

            Yes, Southern California is known to be exceptionally dirty. “There will be exceptions” is a laughable understatement. I stumbled onto this article and am amazed at the people who are blithely, like, “I’m so proud of myself I never clean by solar panels.” Why did they spend the money in the first place? Can’t they be bothered to do a little test of their own? Yikes!

          • Bob_Wallace

            Many of us have solar panels. We’ve made our own observations.

            And we are able to read the actual studies.

    • JHoughton1

      You’re crazy if you don’t clean more often than that. Do a little research, check the output on a clear day, then clean them and check them at the same time next day. See all the electricity you were wasting?

  • Joe Real

    In case of snow, a wiper blade mounted on PVC pipe can be used to wipe off the snow without climbing the roof. Snow will significantly stop electricity production in full sun.

    • Bob_Wallace

      You don’t get much snow… ;o)

      My panels are ground-mounted. A couple of times I’ve had to dig down to find them. Having to shovel off lots of snow is common.

      I clean off my panels with a plastic bladed grain shovel, then a broom with stiff plastic “straws”, and then scrape off the ice….

    • What if you get 8 feet a year like we do?

      • Aquarama

        We get six feet of snow regularly, too

  • Joe Real

    If you have your roof “leased” to Solar City and other companies like them, don’t even bother looking to check your panels, they will be monitoring and doing it all for you.

Back to Top ↑