How Does Snow Affect Solar Production?

Pictured above: Snow on the NYSSF office.

It is that time of year again. The time of the year when we have to heat up our cars and turn the defroster on, shovel out our walkways and porches, lay down plenty of salt, clear our driveways with a snowblower, and fix our poor decrepit mailboxes which have been mercilessly pushed over by the public snowplows. Yes, Winter does bring its challenges. If you are one of the thousands of households in New York State with a Solar Array installed on your roof or in your yard, how will snow fall affect your energy production? After all, at a time when you sorely need the extra energy production to power your space heaters and electric blankets, can you count on Solar during these cold Winter months? I hope this blog post will adequately answer those questions and more.

The first issue we will consider is snow fall. At the time of my writing this post, the Hudson Valley was blanketed in over a foot of densely packed snow. While this may provide the perfect conditions for a snowball fight or a nice weekend at the Ski Resort, it certainly doesn’t bode well for your nice high-tech Solar Array does it? It is true that you need Sun to generate electricity; but you may be surprised by the affects of a layer of snow on your Solar Panels. The Solar Panels themselves are constructed of glass and aluminum. Over 98% of the surface of the panel is glass (the side facing the Sun). If you’ve ever seen a parked car with a layer of snow on it, you probably noticed that the snow on the windows melted at a much greater rate than the surrounding metal surfaces. The same principle applies to Solar Panels. When the Sun comes out and shines brilliantly on a beautiful Winter day, it is actively melting the snow off from the surface of the Solar Panel. The glass below the snow heats up and the snow runs off cleanly; the same also applies if there is a layer of ice. You may even notice the snow bunch up on the lower part of the panel, that is the Sun doing its work. The actual angle at which the Array was mounted also contributes to this effect, so even gravity is on your side.

While the above paragraph is factual, it does not mean that the Solar Panels will operate at 100% when the panels are covered in snow. In fact, they may not operate at all. Snow means shading, and shading is bad for Solar Panels. However, once the snow and ice have melted off of the surface of the panels over time, all systems are a go. Because of the cold temperatures, Solar Panels will actually produce more energy than during the hot months. Why is this? Quite simply, electronics function better in the cold due to a little electrical principle called “Resistance“.  When a physical material is hot, its atoms are excited and move about more freely. While this may sound great, the movement of the atoms actually hinders the free flow of electrons (increasing the resistance). On the other hand, when a material is cold, the atoms are stagnant and still. This allows the electrons to flow freely, unhindered (decreasing the resistance). That is why Solar Panels should produce more energy during the cold-but-sunny days. Adding to this, snow is white. Obvious though that sentence may be, it means that significantly more sunlight is reflected from the ground. More sunlight hitting your panels? That can only be a good thing.

The second issue I will touch on is the increase in cloudy days. While we may have our fair share of sunny days during Winter, we also have quite a number of grey, cloudy days. As you probably already know, cloudy days are not good for Solar energy production. It is an issue, but not an issue we weren’t expecting. During the design process of a new Solar System, our design engineer takes into account the weather patterns of the area where the system will be installed. Many years of carefully recorded weather history is available on the internet. (I should mention that the weather history includes snow fall measurements.) So when we use this extensive information and calculate it, we will have a really good idea as to how much energy your system will produce during the cold Winter months. Overall, this is all factored in your expected yearly production.

The third issue has to do with weight. Snow is heavy, very heavy. How do Solar Panels fare under the weight? This is a good question, especially when you consider the fact that hundreds of pounds of pressure can be applied in just a couple square feet. While it is a valid concern, it is not a significant one. SunPower panels are among the most durable panels ever manufactured. They can take the weight of snow pack in a stride. Not only this, but they are also impact tested. So even light hail should not damage them. And if for some reason damage does occur, SunPower has you backed up with a rock solid warranty. If your roof can handle the weight, so can the panels.

Hopefully, this blog post has answered some of your questions. If not, feel free to email me at info@nyssf.com. Also, please contact me with any suggestions for future blog subjects. I would be happy to write an article on the subject if I feel it would be helpful! If you have an interest in Solar, give us a call at 845-255-0610 to receive a free quote. For now though, thanks for reading!

 

Writer – Ethan J. Powell

 

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