Featured Solar FAQ: What should I do about snow on my solar panels?

snow on solar panels in Vermont“The first winter with our new solar panels, I went out after every snow storm and meticulously cleaned off our panels.  It was so exciting to have them!  But after the first month, I lost steam and didn’t get around to it.  At that point I realized that the difference in electricity production was just really minimal.  So, I haven’t bothered since.”  

-Gaye Symington

Hey, it snowed on my solar panels…

Most of us are thrilled with the snow that’s fallen across our beloved Vermont.  Yet we’ve heard questions from some solar homeowners about the effect of snow on their systems.  So we thought we’d share with the entire SunCommon family what’s up with snow and solar.

Should I remove snow from my solar system?

We recommend against getting up on your roof to wrestle snow off your panels.  The panels are dark and gather enough sun soon to melt the snow, which will slide off the slick glass surface.  Swinging a rake or shovel up there could harm a panel or catch on a roof-mount.  And of course the warranty doesn’t cover damage caused by the homeowner.  Plus, getting up on a snowy roof would risk your getting hurt, which nobody wants.

But aren’t they supposed to be making electricity?

Between the scant sunlight during our short winter days and the occasional snowfall, Vermont’s cold months don’t yield much electricity compared to the power that pours off your roof from the bright summer sun.  So no, after a big snowstorm, we don’t expect the panels to be producing.  Remember that the way “net metering” works is that you store up credits for the power you make and then draw them down when the sun isn’t shining.  When SunCommon’s engineering team designed your system and determined how much electricity it will produce, we factored in the amount of sunlight Vermont homes receive over the course of a year and took account of snowfall.   You’ll catch up when the sun again shines brightly.

Well, what if I want to squeeze all the electricity out of them that I can?

You’re of course free to knock yourself out.  But for all the effort and danger of clearing off your panels maybe a few days before Mother Nature would do the work for you, they’d generate the equivalent of only a partial day of summertime electricity production.  Again, your system was designed with our winter darkness and snow cover in mind.

38 Responses to “Featured Solar FAQ: What should I do about snow on my solar panels?”

  1. eric filkowski January 5, 2013 9:44 am #

    Great feel good story, would have been nice to be made aware of this going in though

    • Don Dockter January 7, 2013 11:30 am #

      Yes, especially after I spent all weekend with a snow broom rake to get the snow off. I also have sat. tv, that technician recommended to spray the dish surface with Pam (cooking spray) or the stuff you can spray on your windshield. Is this advisable???

      • Clary Franko January 7, 2013 1:03 pm #

        We’ve certainly been trying to make everyone aware of this, sorry that the information feels late in coming. It’s good news though, right? No need to spend any more time cleaning the snow off you panels!

        We do not recommend using cooking spray or any other spray to keep your panels clean – these products will cloud the tempered glass surface and decrease production. Enjoy!

    • Bill Mayo January 6, 2014 5:46 pm #

      I lease my equipment. I contacted Sunpower and they advised me
      to not touch my unit because if I damaged it it would invalidate my
      warrantee. Besides, with a production guarantee why would some
      one want to take a chance just to get a little more juice out of the
      system? It can be out of service for an extended amount of
      time in the dead of winter and I would still get paid!

  2. Rachel Seremeth January 7, 2013 10:00 am #

    We haven’t produced anything since 12/26 – nothing at all.

    When we asked the question of both the SunCommon and the installation teams, we were told by both independently that the pitch of our roof combined with the black panels will ensure that they’ll really stay quite clean. I agree with Eric that I would have preferred to know the info above prior to our big snowfall as I’ve been quite stressed about it.

    Don’t get me wrong, I’m thrilled to have the snow and I hope it keeps coming, but I also want to be making power.

    • Clary Franko January 7, 2013 1:08 pm #

      Sorry this has been stressful Rachel. The snowstorm during the holidays was a big one and that’s just part of having solar in Vermont. Don’t worry about the loss of production, this summer will more than make up for it and next year you’ll be able to rely on the credits you built up instead of worrying about a few lost days in January. Now enjoy the snow and don’t worry about your panels – they’ll turn back on soon enough!

  3. Doug Varney January 7, 2013 10:05 am #

    As I recall, much of this was covered in introductory discussions. Part of my reason for getting this solar system relates to understanding in a very intimate way how much energy comes from the sun. I opened up our south facing forest a bit to invite as much light as we reasonably could in the winter. I enjoy comparing the PAC voltage before and after clearing the plates. If I took the time to calculate how much I income “earned” by doing this, I would laugh but that is true about lots of things I do ;-) Your point about the risks of falling off a 2.5 story roof onto a frozen driveway is well taken but it is so much fun standing up there in the sunshine. .. I gotta go plow again and probably clear the plates for this afternoon’s sunshine.

    • Clary Franko January 7, 2013 1:11 pm #

      Thanks for your input Doug! Keep enjoying that snow and stay safe while you re-plow and clear your panels!

  4. Clay Colt January 7, 2013 10:11 am #

    The solar installer who put our PV panels on our roof in June 2009 told us that the system would produce electricity even more efficiently on a clear (snowless) day in the dead of winter when the sun is shining, because there would be less energy lost from the high temperatures of the panels on hot summer days. This sounded logical and makde sense. How true is it? It is is also true that there are fewer hours of sunlight in the winter months. A realistic assessment of solar PV potential in the winter would be helpful. It’s a dis-service to over-sell solar. It is a valuable and realistic part of the total enetgy solution to a carbon-based energy economy. Conservation and thorough insulation and ventilation are also important in the overall plan. Efficient heat/furnaces and thermostats are also very important during the long cold winter months.

    • Clary Franko January 7, 2013 1:15 pm #

      Hi Clay, yes that installer was right – solar panels do produce better at cooler temperatures! Hot hot heat is hard on electronics. Even with that fun fact though, the shorter days, snowfall, and less direct sunlight are real factors in determining winter PV potential in Vermont. We don’t specifically calculate winter vs summer production for our customers but we calculate year-round production so that you can count on your over-production during the long, summer days helping carry you through the winter. This is thanks to our ability to net meter with the utility companies!

  5. Julia Roberts January 7, 2013 11:06 am #

    Thanks so much for this info–the same as we received upon being one of those households who called on this. Yes indeed, most of us are eager to squeeze every drop of sunlight out of our panels, but certainly understand the possible damage and safety issue–and concur–though it’s sometimes hard to choose head over heart!

    • Clary Franko January 7, 2013 1:22 pm #

      It’s great to hear that you’re so excited by your panels and watching them produce! It is hard to see the sun shining and know that they aren’t producing power – but our time and safety are valuable too so don’t worry, just let the sun do it’s trick to melt the snow!

  6. Gary Beckwith January 7, 2013 3:33 pm #

    It might help to quantify what we’re talking about here. There’s a really cool tool online called PV Watts. It shows how much sun (called “peak sun hours”) there are, on average, for each month of the year in our area. You can input your array size and get the estimated output per month. Check it out here:

    http://rredc.nrel.gov/solar/calculators/pvwatts/version1/US/Vermont/Burlington.html

    From the output of the tool, you can see that the year round average is 4.3 peak sun hours per day. The highest month is about 5.5 peak sun hours per day and the lowest month (obviously winter) is about 2.2 peak sun hours per day. As a general rule of thumb, there’s about twice as much sun in a summer month than a winter month.

    Let’s just say hypothetically that your array is completely covered with snow for half of December, all of January, and half of February (and this is not out of the question). If you do the math on the PV Watts website, that would cut about 14% of your annual production. That’s nothing to sneeze at but also not worth risking your back over.

    To further quantify, the PV watts data shows that each month provides about this percentage of the total yearly output of an array:

    January 7%
    February 8%
    March 10%
    April 10%
    May 10%
    June 10%
    July 10%
    August 10%
    September 9%
    October 7%
    November 5%
    December 4%

    I think every installation should be looked at individually. If your modules are within easy reach, there are snow rakes available that are specifically made for solar panels and will not damage them, and it’s not a bad idea to get that snow off there. It’s true — the lower temperatures means higher output so you can get some good power in the winter.

    One thing people should realize — snow is usually worse than most people expect. It’s not uncommon to have your panels covered with snow for weeks at a time if you don’t remove it yourself, regardless of the tilt angle or the color of the cells. the optimal tilt angle for our area is 45 degrees. I’ve installed modules at 60 degrees and they still hold snow. Also I find the color of the cells has very little affect. The fact that they’re black doesn’t mean very much when they’re buried under a foot of snow. Another thing to keep in mind is that the snow can’t slide off by itself if it doesn’t have anywhere to go. So only if your modules are mounted at the front edge of your roof can you hope to have a lot of self-sliding snow action.

    Hope that helps!

    gary (aka the Solar Bus Guy)

    • Clary Franko January 8, 2013 4:42 pm #

      Hi Gary, thanks for putting together all of this helpful information for everyone! We design each household’s solar system to meet their needs for the entire year so yes, understanding the variability in monthly production as seen using the PV Watts tool is valuable, but folks should not be concerned by lower production now as during the summer months their systems will more than make up the difference.

      One thing to note is that people who have leased their panels do not technically own them so we cannot recommend that you clear the panels and it is dangerous to do anything that could possibly scrape them.

      Thanks again Gary!

  7. John Carolin January 7, 2013 4:07 pm #

    The matter of solar panel performance since snow started accumulating has obviously become a big point of conversation/concern for those of going through our first winter. I’d like to add a couple of comments and concerns to the discussion…

    To Doug’s comment about falling off a roof: I’ve swept my panels once, and if that was all it would take, no problemo. However, given this “typical” winter it would be crazy to think about expending that kind energy and taking that much risk keeping the panels producing on a regular basis. Additionally, the fact that my system was installed with central inverter means that even the slightest bit of snow left on the panels will greatly reduce (if not completely) stop production. I wonder if micro inverters were considered in the design process?

    To Rachel’s point: I too asked the question about snow accumulation, and received the same response, “the panels will heat up an clear themselves.” I’ve seen enough winters to have suspected this might not be the case and lo and behold, they don’t. Too much snow at one time, not enough bright sunny days, Welcome to winter in VT. Now the question becomes will the “on-line” days be sufficient to make up for 3-4 months of loss? We shall see, but should this not be the case, I’ll be very disappointed in the engineering/assessment process.

    Which leads me to… For me as a consumer 4 months into a 20 year lease, I’m concerned about the possibility of actually adding to my utility costs if the annual production doesn’t meet the projected production. Has SunCommon given any thought addressing this potential issue for those impacted?

    • Clary Franko January 8, 2013 5:08 pm #

      Hi John, thanks for adding your comments and concerns. Let me try to address them individually.

      First, we did consider using micro-inverters but decided to stay with the tried and true technology of using a central inverter. They have better warranties and the technology has been around longer. What we ultimately want is to provide the most durable, best product we can while making it affordable for the average Vermonter.

      As to the snow accumulation question, we are certainly losing days of production here and there with the heavy snowfall but it won’t add up to whole months being lost. We use local meteorological data from the National Solar Radiation Database to design each system based on your electricity needs, the orientation and other factors of your roof, and the local weather that will be affecting production such as snow, cloudy days, etc. Hope this helps ease your concern about winter production being low.

      As for your last concern, we absolutely have given much thought to wanting to save homeowners money by going solar – not supplying you with an additional bill. I’ll check in again with you in a few months to see how your system is producing when the sun is higher in the sky and since you are under lease SunPower will look at your total production at the end of your first year to hold to their production guarantee. Don’t let this snow storm make you lose faith in your solar system, it will take care of your needs!

      Please let me know if you want to talk further about these concerns, you know where to reach me!

  8. anthony zarriello January 7, 2013 5:40 pm #

    I take a very soft window washing pad and a extension pole and clear a very small corner of 1 panel to expose the black surface. This accelerates the melting process.

  9. ellen maxon January 7, 2013 9:25 pm #

    I was thinking about spraying warm water on the panels with a power attachment – hooked up to a garden hose??? No climbing on roof – I hate seeing these sunny days and no progress with the snow sliding off

    • Clary Franko January 8, 2013 4:47 pm #

      Hi Ellen, how did your panels do today? Did the sunny day melt the snow finally?

      The risky thing about spraying your panels is that if the temperature goes below freezing again while the panels are still wet the same vicious cycle will start over. Good idea, but we still encourage you to try to be patient and understand that the loss in production during these winter days is nominal compared to what your system will produce during the long, summer days. Until then, just enjoy the snow!

  10. Lucas Tremble January 8, 2013 11:16 pm #

    Just a thought, what if this recent major snow event wasn’t a “Nor’Easter”, and the wind wasn’t blowing snow from the north and causing it to pile up on our southern exposed roofs. We can’t control everything, especially mother nature. While I personally don’t care how much snow we get, because where I live it usually blows off my roof within a few days. I was curious if there is a way to install a defrosting element on top of the panels to jump start the melting process without damaging or reducing their efficiency.
    By the way, did anyone catch the crescent moon pulling the sun up this morning? Pretty cool.

    Thank you Clary for responding to everyone and keeping us all engaged.

    • Clary Franko January 9, 2013 1:05 pm #

      Thanks Lucas! The technology that you’re designing with your brainstorming would be a smart way to clear your panels I imagine, but for the tiny bit of extra production you would get I don’t see it ever being cost-effective. The largest amount of your production comes from times that snow and ice aren’t around.

      Missed the crescent moon, sounds like quite a site!

  11. Will Wolcott January 9, 2013 7:46 am #

    Sitting here on a sunny day I can’t help but to think that there must be a way to safely remove snow from my inactive photovoltaic solar panels on the roof of my second story house. They haven’t produced power since Dec 22 2012, there buried in about 16” of packed snow. Mother Nature has a lot of work to do. Is it possible to install a low voltage heated mat on the underside of each panel, a mat that is laced with thin wire that when energized will generate heat, similar to the ones used under bathroom flooring? Another idea is to install a solar water panel alongside the PV panels and install tubing on the underside of the photovoltaic panels, and using a PV powered pump circulate heated water through the system to melt the snow. This system could be tied into the home owner’s boiler or domestic water heater to assist the panel on dark days or at night. These heaters could be manually controlled by the home owner. I know that it will take some energy to do this, but it’s better than letting the PV panels remain buried in 16” of snow for several weeks. I have a neighbor who has a solar water system and he has the system set up so that when his panels are buried under several inches of snow, he can reverse the flow and send warm fluid up to the panel and after a few minutes the snow slides off the panel. Is this a feasible idea?

    • Clary Franko January 9, 2013 5:44 pm #

      Hi Will, I understand how much it pains you to see the sun shining and not be producing any power – but alas, I don’t think that the cost-benefit analysis of this systems you’re brainstorming would be a good one. If only it were as simple as with your neighbor’s solar hot water system. There just isn’t a silver bullet to this one unfortunately. Hope this helps!

  12. Peter Youngbaer January 6, 2014 4:37 pm #

    We have been extremely concerned about the lack of production that last week of December.
    We have two field=mounted panels. Santa Claus finally brought us an aluminum roof rake with a very nice soft edge. As the top of our panels are 24 feet off the ground, this rake worked great. It took only about 15 minutes to clear off all the powder but a thin coat. The sun took care of the rest quickly. However, in the interim, we got our highest electric bill ever from our utility. We were very disappointed that our installation took a long time (we signed up in April, were told the installation would take place in July, but were not commissioned until mid-October.) Thus, we lost the three prime generating months that would have built us up credits for the winter months. We were also told that we would be instructed on how to clean the panels, and indeed, were even asked in a survey whether or not that instruction had occurred. We said no, and have still heard nothing. The only on-line advice I could find was similar to a comment above: “Don’t worry, the sun will take care of it – especially if even just a corner of a panel is exposed..” Too much flowery over-selling, in my opinion. So, rather than sitting idly by, we cleared the panels. Yesterday morning in just two hours, we generated more than the prior week. Since we’re in the hole from the delays in installation and didn’t generate sufficient credits to get us through the winter, I most certainly will get out there and clear the snow and make the most of what we get from the sun.

    • Kevin Lehman January 6, 2014 6:24 pm #

      I am sorry for your frustrations, Peter. We are getting systems installed and turned on much more quickly now, but I know that doesn’t help with your lack of utility credit. But hopefully this spring / summer / fall will more than make up for it.

  13. Rob Moran January 6, 2014 6:09 pm #

    Panels were installed in late April of 2013. My wife and I went into this with the understanding that we needed to build up a credit to get us through the winter months. I am very happy with the amount we have been able to produce. Don’t get me wrong, when that sun is out and I turn on my app and it says 0.0 production, I feel annoyed. To help my panels clear themselves off I usually shovel the bottom of my roof off just under the panels and let gravity do the rest. It may take a day or two and some sun to get it started but usually the snow slides off. Then we have another snow fall and I’m back at it. I will continue to do this all winter with the hope that I can grab a few more KWH. No matter the case, my wife and I made the right decision with solar and we are happy.

    • Kevin Lehman January 6, 2014 6:25 pm #

      Rob: Glad to hear you are happy with your solar!

  14. darryl kuehne January 6, 2014 8:24 pm #

    I purchased a 30 Foot Heavy Duty Telescoping Pole from Unger its made in Germany and has a soft brush attachment for clearing snow off solar panels. I gotta make power when the sun is shining. oh yea roofrake.com not cheap but should pay for itself eventually.

    • Kevin Lehman January 7, 2014 11:05 am #

      Thanks for sharing this, Darryl.

  15. John Hadden January 7, 2014 7:45 am #

    We have a pole mount system in our front field. I purchased a “soft roof rake” from roofrake.com, and have been cleaning the panels after each snowfall. It takes about 10 minutes, and when the sun shines, we make power. Here’s a link to the roofrake site:

    http://roofrake.com/Productpages/snowpro2.asp

    Cheers, John

    • Kevin Lehman January 7, 2014 11:04 am #

      Thanks for sharing this, John. And glad to hear you found a solution that works for you.

  16. Macy Moulton January 7, 2014 10:29 am #

    We’ve had our panels for over a year (installed October 2012). I did fret over those beautiful
    sunny days after snow storms, when our panels seemed useless, but the risk of damage, seemed too great to mess with them. The sunny days later in the year built up credits, which this year we get to use to offset winter power costs. I had estimated in October 2013 that for
    the year we had come pretty close to the expected yearly power production. Close enough for me to be happy. Suncommon sent us an e-mail a month or to later that we were $6.00 short
    of the predicted amount. Definitely not worth, braking the lease, or my back over that.

    • Kevin Lehman January 7, 2014 11:02 am #

      Hello Macy. Thanks for sharing your story and we are glad you are happy!

  17. Mark S. Meritt January 16, 2014 9:02 am #

    This is our first winter with solar panels, and while we’re certainly interested in production, we’re also concerned about safety. We had no idea there would be sudden avalanches, and it’s an injury risk for our front door entrance way. Snow guards would help that but would keep the snow up longer, further hurting production. A roof rake can get the snow down in a controlled way while speeding up production but is obviously some amount of time and effort. We’re wondering if a small porch with roof pitched down to either side would help. We’d let the avalanches happen on their own, but with the hope that the porch would deflect snow away from the entrance path. Or perhaps we’re wrong and the avalanche would just coast right across and end up in the entrance path anyway. If it would work, though, it could cost less to install than snow guards and would mean better production than snow guards, even if the production wasn’t as good as manually clearing the panels. Any insights?

    • Kevin Lehman February 7, 2014 9:08 am #

      Hello Mark and sorry for the delay in responding. It’s hard to make a recommendation in this case without seeing your set-up, but it sounds like the porch should work fine as long as the pitch was steep. Of course, there may be some storms where ice builds up and prevents the snow from sliding off.

      Good luck with your project and your system!

      – Kevin

      • Mark S. Meritt February 7, 2014 2:10 pm #

        Thanks for the reply, no worries about the timing. I hope that it won’t turn out that the snow’s momentum just carries it forward!

  18. lapabc January 23, 2014 9:24 pm #

    Sorry, but I really did not like the “hey everything will be okay” tone because things are different for different people. Providing people what real options would have been much, much better.
    .
    I have a PV array of black Sunpower panels on a fairly steep roof… and yes if I leave it alone the snow can melt and slide off on its own — sometimes. But the house has a main roof with a cross gable that creates a valley the runs near the PV array. After heavy snows the asymmetric build up of snow prevents the blanket of snow from cleanly sliding off the array, leaving as much as one third of the array covered on one side. To make matters worse, the way the array is configured and the panels are ganged together, if that third is covered, the whole array doesn’t produce anything. Today, in fact, I looked at our output and my 4.5 kW array was producing 9 watts… yes, tens of thousands of dollars of PV panels fully illuminated by the sun producing enough electricity to power a couple night light. EVENTUALLY the snow will slide off, but with cycles of partial thawing and subfreezing temps the array could remain CRIPPLED FOR WEEKS with hardened snow pack that covers only a quarter to a third of the array while the sun beats away on the rest.
    .
    When this happened the first winter of our array, I got on a ladder and using a push broom cleared away the bottom part of the snow pack so the whole thing could slide off the roof entirely when the sun did its job. Clearly I couldn’t do this all the time, so like other people posting comments I found a soft “roof rake” with extension poles. I don’t need to clear the whole array, just the bottom part near the valley on my roof… and I don’t need to bother with light snows. (and not to offer an endorsement but just information, the place I started looking was here: http://roofrake.com/Productpages/snowpro2.asp)
    .
    Bottom line, sometimes it’s okay to leave it alone but sometimes it’s not. Provide people with FULL information so they can use the options that are best for them.

    • Kevin Lehman February 7, 2014 2:33 pm #

      Thanks for sharing how you tackle snow on your panels. You’re right; lots of people have different situations, rooflines and pitches and we’re glad you found something that works well for you. Soft roof rakes are certainly safer than climbing on the roof! We appreciate your comments.

      – Denise

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