Many people assume solar only works in hot, sunny places. It is an easy mistake. Solar panels run on light, not heat. A cold, clear day can be one of the best days of the year for each hour of sunlight.
Winter does cut your output, though. The days are short, the sun sits low and snow can cover your panels. This guide explains what really happens in winter, how much power you can expect and why solar still makes sense in cold places.
Do solar panels work better in the cold?
Yes, for each hour of sun. Solar panels lose efficiency as they get hot. Most panels lose about 0.3% to 0.4% of their output for every 1°C above 25°C (77°F). This number is called the temperature coefficient, and you will find it on the panel's spec sheet.
Here is a worked example. On a summer day your panels heat up to 60°C (140°F). That is 35°C above the test temperature.
- 35 × 0.35% = about 12% less output than the panel's rating.
On a cold, sunny winter day the panels might sit at 5°C (41°F). That is 20°C below the test temperature, so they can make a few percent more than their rating for the same amount of light.
So why is winter output lower? Because the amount of light is lower, not because of the cold.
Why do shorter days matter so much?
Two things shrink your winter output. First, there are fewer hours of daylight. Second, the sun is lower in the sky, so its light passes through more air and hits your panels at a sharper angle.
Solar experts use a measure called peak sun hours. One peak sun hour equals one hour of full, strong sunlight. A summer day in a northern city might give 5 to 6 peak sun hours. A December day in the same city might give only 1 to 2.
A quick worked example for a 6 kW system:
- Summer: 6 kW × 5.5 sun hours × 0.8 (real-world losses) = about 26 kWh a day.
- Winter: 6 kW × 1.5 sun hours × 0.8 = about 7 kWh a day.
That is a big drop, but it is not zero. And you plan around the yearly total, not one month.
What happens when snow covers the panels?
A thick layer of snow blocks almost all light, so a fully covered panel makes almost nothing. The good news is that snow usually does not stay long.
Panels are smooth glass set at an angle. Once a little sun gets through, the dark cells warm up and the snow starts to slide off. On a steep roof, panels often clear within a day or two after a storm. Flat or low-tilt panels take longer.
Snow can even help a little. After the panels clear, white snow on the ground reflects extra light. This matters most for bifacial panels, which collect light on both sides.
Researchers at NREL and elsewhere have studied snow losses. In snowy places, yearly losses from snow cover often land in the range of a few percent up to around 10% or more, depending on tilt and how much snow falls. Most of that loss happens in months when output is already low.
How much power do panels make on cloudy days?
Clouds cut output, but light still gets through. How much depends on the type of cloud.
| Sky condition | Rough output vs. a clear day |
|---|---|
| Clear sky | 100% |
| Thin or broken clouds | 50% to 80% |
| Mostly cloudy | 25% to 50% |
| Heavy overcast or rain | 10% to 25% |
Sometimes panels make a short burst of extra power when the sun pops out from behind a bright cloud. This is called the edge-of-cloud effect. It does not change your yearly total much, but it shows how sensitive panels are to light.
How does winter output compare in a northern vs. southern city?
Let's compare a 6 kW system in two places: a northern city like Minneapolis and a southern city like Phoenix. These are rough estimates based on typical sunshine data and normal system losses. Your real numbers will depend on your roof angle, shade and weather.
| Month | Northern city (approx. kWh) | Southern city (approx. kWh) |
|---|---|---|
| January | 390 | 720 |
| February | 500 | 780 |
| March | 690 | 950 |
| April | 780 | 1,040 |
| May | 860 | 1,100 |
| June | 880 | 1,070 |
| July | 900 | 1,020 |
| August | 830 | 1,000 |
| September | 680 | 930 |
| October | 520 | 860 |
| November | 340 | 730 |
| December | 290 | 660 |
| Year total | about 7,660 | about 10,860 |
A few things stand out. The northern system makes about three times as much in July as in December (900 ÷ 290 = 3.1). The southern system's swing is much smaller (1,020 ÷ 660 = 1.5). Over a full year, the northern system still makes about 70% of what the southern one does (7,660 ÷ 10,860 = 0.71).
If you have net metering, extra summer power can earn credits that help cover your winter bills. Learn how that works in our net metering guide. To estimate output for your own home, try our system size tool.
If Germany can do it, can you?
Germany is one of the world's biggest solar markets. Yet most of the country sits farther north than any of the lower 48 US states. Berlin is at about the same latitude as southern Canada. Winters there are gray and short.
Even so, Germany gets a large share of its electricity from solar in a typical year, according to IEA data. Millions of homes there have rooftop systems or balcony panels. If solar works under German skies, it can work in most of the US.
The key lesson from Germany is that solar does not need perfect weather. It needs enough sunny hours across the year, fair power prices and a good grid connection. Your state's rules matter too, so see our state solar pages.
How do you get the most from solar in a cold climate?
- Size for the year, not the month. Do not try to cover your December use with panels alone. That would mean a system far too big for summer.
- Steeper tilt helps. A steeper angle catches more of the low winter sun and sheds snow faster.
- Watch for winter shade. Low sun casts long shadows. A tree that is no problem in June can shade your roof all of December.
- Think about a battery for outages. Winter storms can knock out power. A battery can keep key loads running. Our battery sizer can help.
Frequently asked questions
Do solar panels work at night?
No. Panels need light to make power. At night your home uses grid power or energy stored in a battery.
Can snow damage solar panels?
Panels are rated to handle heavy snow loads. Most damage comes from people clearing snow with metal tools or walking on panels, not from the snow itself.
Is solar worth it in a cloudy state?
It can be. Your yearly output will be lower than in a sunny state, but high power prices and good net metering rules can still make the numbers work. Run your own estimate before deciding.
Should I clear snow off my panels?
Usually no. Snow slides off on its own within a day or two on most tilted roofs. If you do clear it, use a soft foam rake from the ground only.
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