I love my solar panels, but how much power do they produce when covered with SNOW!?
Since we’re now going into our SECOND winter with solar, let’s find out!
First off, YES! Solar panels DO make more power when they are cleared of snow! As you can see in the first video, clearing the snow has an immediate effect of allowing the panels to make more power. It’s also interesting that the panels still covered with snow do produce SOME power. Although it’s greatly reduced, some sunlight makes it through the snow.
Just based on those numbers, it seems like it should be a “no-brainer” to always clear the solar panels immediately after a snow-storm. But it’s actually more complicated than that. Through both weather records and personal observation, I can see that in my area, snow-storms are usually followed by days of VERY HEAVY CLOUD cover. I’ve recorded days as low as .21kWh of total production just from it being cloudy!
One kilowatt-hour of energy is worth 13 cents to me. So, .21kWh would be the economic equivalent of LESS than three cents! The economics of a VERY HEAVILY Cloudy day are terrible. Fortunately, they tend to average out with nice days. However, those cloudy days tend to stick around right after a snow fall. Even if I clear off the snow, it might be only to collect the equivalent of 3 cents per day in energy!
On the other hand, a good, clear, bright, sunny winter day might mean I produce about 20kWh of energy. That’s the equivalent of $2.60.
RISK VS REWARD
The other consideration would be “What does it take to clear the panels?”
For a ground-mount system, it probably means just a little exercise and a push broom. It’s relatively straight-forward to clear the snow. For solar panels mounted on a roof, a person might need to use an extendable “roof rake”, stand on a ladder, or go onto the roof itself to clear the snow. This does present a risk. Slips and falls are always a risk working higher up, but they are even more exaggerated with snow and ice are involved.
SUCCESS THROUGH DESIGN
Probably the best approach to making a solar system produce well, even in a snowy winter, is to make sure it’s steeply angled. The steep angle helps prevent snow from accumulating, and easily slide off if it does.
Roof mounted panels are typically installed at the same angle as the roof, so a steep roof is ideal to help the panels shed snow.
Ground mounted panels also have an advantage in that they are sometimes designed for adjustable tilt. Twice a year, spring and fall, the owner will tilt the panels from a more flat angle to a steeper angle. The flatter angle points the panel more straight up, maximizing summer solar production. Titled to the steeper angle, the panels help with winter solar production, but also help shed snow.
MEANWHILE, AT THE SOLAR GARAGE
It’s been our personal experience here in south-eastern Wisconsin (at about 43 degrees north latitude) that clearing snow from the panels should just be based on watching the weather report. If the snow will be followed by days of solid clouds anyways, it’s not worth doing at all. If the snow fall will be followed by sun, but not too cold, the sun will melt the snow enough for it to slide off.
Only in the case of snowfall, followed by COLD and SUN is it worth actively clearing the snow. The cold weather makes sure the snow stays in place, preventing it from sliding off. And it sure would be a shame NOT to capture that sun the few days that we have it in the winter!
Ideally, I would have liked our solar array to be mounted steeper. However, it was roof-mounted, and the local building codes and ordinances prevented us from building the garage roof any steeper. As it is, the final slope of the garage is just shy of 30 degrees. On a previous solar experiment, I mounted a solar panel to my daughter’s clubhouse and swing-set. The solar panel mounted to that roof is at 45 degrees. After a snowstorm and some sun, I’m often looking at both the garage and the swing-set comparing how long snow stays on them. The steeper solar panel always clears faster, but by how quickly depends on sunlight, temperature, and the quality of the snow (sticky, fluffy, thick, wet, dry, fine, etc.)
MICRO-INVERTERS
One other thing I’ve realized with snow is that it does act similar to shadows. Even a small shadow across a solar panel can significantly reduce solar production. Snow acts the same way. My system uses micro-inverters so that each panel is independent of the others. I decided on that system because I have some late-day shadowing from a neighbors trees. What I hadn’t realized is that it also helps with snow. As snow is melting off the panels, it might cover certain panels, but not others. Since each panel is independent, the ones not covered by snow keep producing at maximum power.
I have a friend in our area who has a similar size solar system, but his is a traditional single inverter, with all solar panels connected in series. Partly blocking even one panel reduces the power of all of them. After a snow storm, my solar consistently outproduces his.
OUR TAKE-AWAY
Yes, snow can definitely reduce solar output in the winter. But we also have to keep in mind the greater weather patterns, especially in areas that get extreme winter clouding. Smart design, such as steeply angled panels and micro-inverters help passively maximize solar production.
Manually clearing snow is certainly possible, but a person also needs to think about the risk and reward of it. I’d be happy to get a little outdoor winter exercise standing on the ground and clearing snow with a roof rake AND collect $2.60 per day in energy. I’m much less likely to want to stand on a ladder or climb a roof in the cold, and risk injuring myself to earn a measly 3 cents!
If you live in an area with regular winter snowfall and are considering installing solar, go for it! Just keep in mind what we’ve just mentioned about snow. Of course, it can make a big difference whether you live in Chicago, IL versus Buffalo, NY, so you always want to design your system as appropriate for your area!
To learn more about our solar garage: LINK
See how much power we are making, anytime, at the public data.
Until next time, stay charged up!
-Ben Nelson
