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Do Solar Panels Work in Winter?

As the days have started to grow noticeably shorter, thoughts of the coming winter creep into mind. In the mid-Atlantic area, winter can be a dreary time of year. It gets dark earlier, and temperatures get frigid. Many people wonder what effect this has on solar production. Do solar panels even work in the winter? In this post, we’ll go over some of the things that you should know about winter solar performance. We’ll discuss examples where solar harvest could be bad, but mostly we believe you’ll be surprised that the performance will likely be better than you are expecting.

The effects of cold and dark on solar panels

We’ll start with the bad first because it’s likely not as bad as you may think. Obviously, the significantly shorter days will reduce the amount of time that your solar panels are exposed to sunlight. This is going to lower the maximum amount of power that they can produce in a given day. The good news is that it is also usually cold in winter. Yes – that is good news! Many people are under the mistaken impression that solar panels need heat to work. Nothing could be further from the truth. All the solar panels really need is exposure to sunlight. In fact, heat makes solar photo-voltaic cells less efficient. That’s right, the cold of winter will actually increase the efficiency of your solar panels.

In fact, every increase of about 2 degrees Fahrenheit will result in about 0.05% less energy output from a solar panel. Of course, as stated previously, the opposite is true with cold weather. This is great news because the significantly colder weather of winter helps a bit to compensate for those hours that your solar panels are deprived of sunlight. It is important to note, however, that the temperature of the solar panels is not the same as the temperature of the outdoor air. Solar panels tend to be warmer than the ambient environment as they bake in the sun; even during the winter. However, colder air, especially if it’s windy, will cool them significantly as compared to summer time.

Solar and snow

If your solar panels are covered in a couple inches of snow, they aren’t going to work as efficiently. This does not mean that solar does not work in a snowstorm though. In addition to being warmer than the ambient outdoor temperature, solar panels are slippery when wet and positioned to catch the most sunlight. Both of these factors help them resist snowfall or eliminate it quickly. Solar panels are also usually installed at a steep enough angle that helps persuade the snow to slide off. Of course, a lengthy snowstorm will eventually get the best of your panels and diminish their crucial power making ability. For the reasons mentioned above, they should attract enough sun to clear themselves off relatively quickly after the storm stops.

Notice that we said the snow will diminish your power output. It will not cut it off completely until you’ve got at least 3-4 inches built up depending on the density of the snow. That said, even with an inch or two on your panels, some light still gets through and the panels continue making power. In fact, a process known as forward scattering spreads the light out over a larger area as it passes through the snow. You can see a similar effect by shining a flashlight through a sheet of plain glass versus a sheet of frosted glass. This will not negate the loss from the snow cover, but it does help compensate for it in much the same way that the cold weather helps compensate for decreased sunlight hours.

Last, SolarEdge systems have optimizers which enable uncovered panels to make their full amount of power even while most of the rest of the array is still covered in snow.

Average production

After all this, you may still be wondering just how much power you will make in the winter relative to the summer. Sometimes cold hard data is better at setting the mind at ease, so let’s look at some numbers on how a typical 5kW system installed in Maryland performs throughout the year. The data presented is pulled from PVWatts.

In the hotter months, April to September, such a system outputs a range of 641kWh to 571kWh per month. Of those months, July is the most productive at 704kWh. The total production estimated for this 6 month period is 3949kWh.

Now that we have our baseline of the warm and sunny months, let’s take a look at how the colder, darker months of winter fare. The months of October to March output a range of 522kWh to 588kWh per month. November, December, and January are the lowest producing, with December representing 347kWh. Things start picking back up starting in February and March gives us the higher end of that range. The total estimated power output during those 6 months is 2693kWh.

From this data, you can see that the average solar setup in Maryland (and surrounding area) generates about 68% of the power in the winter months as compared to the summer months. While this is a significant drop in output, it isn’t the massive drop that some people expect from the winter months.

Conclusion

Hopefully, you’ve learned a little something about utilizing solar power in the winter. Maybe we’ve even cleared up a few misconceptions. While many people are under the impression that solar is impractical in the winter, nothing could be further from the truth. In fact, there are happy solar-powered homeowners even in the extremely harsh winters of Canada. Knowledgeable installers and high-quality panels will also help boost your efficiency and perhaps get your numbers higher than the averages given in the previous section. In addition, having SolarEdge optimizers can help substantially during partial snow melts.

Mountain View Solar has always been a leader in green energy initiatives. We started our journey as premier builders of energy efficient homes before making the shift into renewable power generation. We take energy efficiency and green energy initiatives very seriously and will help maximize the output of your new solar installation regardless of what month it is.mtvSolar is your local West Virginia, Virginia, Maryland and Pennsylvania contractor.

If you have any doubts about solar as a viable energy source, want more information about winter performance, or are ready to get started on the process of installing solar on your home, contact us today!

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