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Do solar panels work in cloudy weather?

Avatar for Dave Llorens
Published on 05/30/2012 in
Updated 06/27/2019

a picture of solar panels on a roof in some cloudy weatherSolar panels generate the most electricity on clear days with abundant sunshine (not surprisingly). But, do solar panels work in cloudy weather? Yes… just not quite as well On a cloudy day, typical solar panels can produce 10-25% of their rated capacity. The exact amount will vary depending on the density of the clouds, and may also vary by the type of solar panel; some kinds of panels are better at receiving diffuse light. SunPower solar cells, for example, have been designed to capture a broader range of the solar spectrum. By capturing more red and blue wavelengths, their solar panels can generate more electricity even when it’s overcast.

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Read more about solar on a cloudy day here

Ultraviolet light also reaches the earth’s surface in abundance during cloudy days (if you’ve ever been at the beach when it’s cloudy and gotten a sunburn, you’ve experienced this firsthand). Some solar cells are in development that can capture UV rays, although these are not out on the market yet. Even with a standard solar panel on a cloudy day, though, you will be able to generate some power when it’s daylight. The same thing is true in foggy weather. If you live in a city with frequent fog, like San Francisco, you’ll still be able to generate electricity when the fog rolls in.

One cloudy day isn’t as important as the amount of sunshine over a full year…

When you’re looking at how solar power can help you save money on your electric bill, you’ll be considering how much sunshine you get over an entire year, not any particular day. If you’re generating more power than you need, your electric company will look at what you’ve produced over a full year as they calculate how much to pay you. To find out how much solar radiation your house gets (or your location’s “insolation” rating…. here’s a good old school calculator for insolation), visit this handy tool. The good news is that even if you live in a city that isn’t known for its sunshine, you likely still get enough bright light over a year that solar power can make sense for you. Some of the places with the most installed solar, in fact, aren’t known for their sunshine.

Cloudier locations are still a good match for solar

Germany gets only about as much sunshine as the state of Alaska, but Germans have successfully installed about 25 gigawatts of solar power– half of the entire world’s supply. Portland, Oregon is known for its rainy, dreary winters, but is another good location for solar power: over a full year, despite the winter weather, Portland gets as much sunshine as the average U.S. city. Cities like Portland also have slightly cooler weather than average, which is an advantage for solar panels. Because of the electronics inside, solar panels work best when they aren’t too hot. In a city with extreme summer heat, solar is a little less efficient, which is part of the reason why solar panels in cloudy San Francisco can actually produce more power over a year than the slightly sunnier, hotter city of Sacramento.

A silver lining to that cloud: how the “edge of cloud” effect can produce more solar power than a sunny day

If you have solar panels and keep a close watch on your power output, you may have noticed a strange phenomenon: on a partly cloudy day, it’s possible to exceed your solar system’s power rating and produce more power that you could on a sunny day. Known as the “edge of cloud” effect, this happens when the sun passes over the outer edge of a cloud, magnifying the sunlight. The intense light causes your solar system to boost power output temporarily, which can help balance out losses from full cloud cover. Solar installers typically select system components that can handle temporary power boosts of this nature (similar effects can occur when sunlight is reflected off snow or water). If you live in a city with frequent partly-cloudy weather, like Seattle, you may choose to install an over-sized solar inverter to take the best advantage of these power boosts. Sign up with us to learn more.

So, bottom line – do solar panels work in cloudy weather?

Yes, yes they do. But only 10-25% as well. However – this doesn’t matter, what matters is how much sun you get year-round. Cloudy days will come an go, but on the average, it’s not going to effect the return on investment of solar panels at all.

Last modified: June 27, 2019

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Heatercamp
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Recently I installed a solar pool water heating system for my pool. It saves the extra cost to heat pool water and reduce my electric bills. It is very efficient and durable.

Anonymous
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Anonymous

I Have two 200am Batteries with two panell of 125 watts and 30 am charger control but i didnt recieve enough power during night hour can you help me to explain it

Ben
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Ben

Clouds do matter. While it is true for grid-tied consumers that yearly production and peak use production are the main drivers, for off-grid users, cloudy days result in significant challenges to size a system to get through the long rainy winter months without running your generator. For a system that is fine with 300W of panels in summer you might need 1000W to get by in winter, plus the ability to change the angle. “It doesn’t matter” was a bit simplistic, even if I agree with you that clouds don’t mean that solar power is ineffective. cheers Ben

Anonymous
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Anonymous

There are controllers that increase the voltage during overcast periods in the panels and the regulator will produce more amperage after stepping down the voltage.

chinku
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chinku

i have an farming place about 10 arc .and i estimate to a deep borewell in there but there is one problem that is there is no electricity so i will plan to solar system .but i want to know that works on rainy or cloudy climate . plz can u explain my problem or contact me no my np:- 7008779525

Larry
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Larry

Yeah clouds have a dramatic effect on solar, i have on 2x, 300 watt panels on my cabin and i watch the charge controller very closely, and when clouds roll by i am getting something like 15-20% compared to full sun, i think the real idea is to oversize your system to smooth things out for those days (which means increased costs), but overall solar is still an amazing option especially if you are offgrid. But you have to have the money…

RAJU7
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RAJU7

IS IT POSSIBLE TO GENARATE ELECTRICAL ENERGY FROM SOLAR CEL BY USING NORMAL HEAT

Ben Zientara
Admin

No. Photons activate the electron cycle in a photovoltaic cell. Heat actually makes PV solar sells work less efficiently.

Indy
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Indy

The article text doesn’t match the first infographic you link to. Is it 10-25% of their rated capacity, or 10-20% drop in production?

Ben Zientara
Admin

Hi Indy-

We’re sorry it’s unclear. In the infographic, a lightly cloudy day is shown reducing output by 10-20%, while in the blog here, its referring to production on an overcast day. We’ll do our best to make the text clearer. Thanks for pointing out how that was weird.

anonymous
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anonymous

As much sun as the State of Alaska. What does that even mean? Juneau is very cloudy, Anchorage is pretty cloudy. Fairbanks is partly cloudy, but the Arctic coast–Barrow, Prudhoe Bay and the other arctic communities enjoy 80 days of perpetual sunlight with few clouds and no sunset. Like Alaska, Germany does well with Solar in summer. Most people don’t have or use A/C and it is daylight for 18 hours or more. Now, for the sake of completeness, would you do an article on solar performace in these regions from October to April?

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