Solar Panel Performance in Winter?

Solar Panel Performance in Winter?

Did you know that parts of Minnesota get the same amount of sunlight as parts of Texas and Florida? The southern states see more cloudy days and storms that bring the Midwest pretty close to competing with the amount of sunlight they get.

So why not cover the desert in the Southwest with solar panels? The chart begins to explain one of the big reasons… solar efficiency starts dropping efficiency as soon as they get above their optimal operating temperature of 77 degrees Fahrenheit (25 celsius). The Midwest also has enough rain to self-clean the panels. In the desert even a light dusting can totally eliminate solar performance so regular cleaning and maintenance eats away at some of that great solar potential.

So the cooler climate in the Midwest is actually beneficial to solar panels.

Panels have a Black or Dark Blue Finish Because the silicon crystals on solar panels are dark they are naturally going to absorb more of the suns energy. This helps heat up the panels and melt snow if it is sticking to the panel. One advantage to ground mount systems is that you can actually go out and rake off the panels with a cloth wrapped home made squeegee or a pool noodle around a snow rake. When Aquilla calculates it’s return on investments it assumes you are not going to remove snow so it is not necessary. Also the benefit is marginal since the hours of sunlight are low during the winter and is not recommended if there is any risk involved (like climbing on the roof, on a ladder or getting buried when you rake a big pile of snow on top of yourself). We always advise to let the sun do it’s job during the winter and let it melt off the snow and ice on it’s own.

Tilting the panels Only half the reason to tilt the panels is for snow run off. Most of the reason to tilt the panels is to make them line up with the optimal angle of the sunlight throughout the year. If you are in an area that gets lots of snow you might think it’s better to tilt the panels more, but this is not always the case. You might achieve more energy harvest by having them almost flat! You have to look at the whole year. You can capture more of the suns energy during the summer months when we get 8 hours of average sunlight and sacrifice the days during the winter when we only get 2 hours of average sunlight. This is why we have engineers. They calculate the panels tilt by adjusting the racking. In this area a 25 to 35 degree tilt is a pretty good angle.

For some flat roof installations, such as the LAXprint 40kW installation the panels are at 15%, it is a matter of space. For every inch you tilt a panel up, you have to move the next row two inches further back due to panel shading. In most flat roof installations a flatter angle makes more sense since the energy harvest peaks are very high during the summer. In looking at the actual versus the estimated power production below you can see why having panels at a low angle during the summer months have an advantage. It would take weeks of winter production to equal just one goodsunny summer day.

To Clean or not to clean your panels.  During the summer the Midwest receives plenty of rain to keep your panels clean. In fact, you might actually make matters worse because of the high mineral content in the water. When the water in our area quickly evaporates you will leave a film buildup behind that might be worse than any accumulation that was there before from dust and debris.

Keeping the sun access on your panels. The best thing to watch out for is anything that might be blocking the sunlight access to your panels. If there are overgrown tall bushes or trees you might consider trimming them down or even replacing them with a shorter growing variety. If you see shadows from nearby tree branches hitting the panels in the spring, even just a small amount, it would greatly increase your production to trim them back. Even if a portion of a panel is blocked it greatly affects the production.


  • The Midwest has great solar access
  • The frequent rain showers will keep your array clean
  • Don’t wash or hose down your array due to mineral deposits
  • Never climb on the roof to adjust the array or clean off snow
  • If possible trim any nearby growing branches that are shading panels
By |2018-04-16T13:31:14+00:00November 19th, 2017|Categories: Frequently Asked Questions|Comments Off on Solar Panel Performance in Winter?