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Do solar panels work in cloudy weather?

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.

Be sure to check out our cloudy day solar infographic!

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.

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20 thoughts on “Do solar panels work in cloudy weather?

  1. RAJU7 says:

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

    1. Ben Zientara says:

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

  2. Indy says:

    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?

    1. Ben Zientara says:

      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.

  3. anonymous says:

    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?

  4. Bill says:

    Article did not tell the whole story. It doesn’t matter if the panels produce anything if it is not enough to reach the operating threshold of the grid-tie inverter(s) or the charge controller for battery systems.

    1. Ben Zientara says:

      Thanks, Bill; that’s a very good point!

  5. Steve S says:

    “sun passes over the outer edge of a cloud, magnifying the sunlight”

  6. Bill says:

    Will they still work under a tarp which is open on two ends like a hoop, the panels are on an rv?

  7. Anonymous says:

    Where does the 10-25% number come from. Is it just a guess, or is there a reliable reference?

  8. mongweemangtshephang@gmail.com says:

    is it possible for a geyser to use solar electricity and our nomarl power electricity at the same time?

  9. Anonymous says:

    do solar panel generate electricity during rainy season in india

    1. Ben Zientara says:

      Yes, but if it is fully overcast all the time, they generate much less than they would in full sun. What’s really important is the average annual sun your location receives. Look at this map:

      Find the colored region in your your home is located, then multiply the number that represents that region by 0.78 (relative efficiency of a solar PV array, including losses from wiring, inverter, etc). Multiply the resulting number by the kilowatt rating of your array.

      Here’s an example: a 5-kW array in Mumbai would generate 7,215 kWh/year based on the following formula:
      1,850 x 0.78 = 1,443
      1,443 x 5 = 7,215

      Now it will certainly generate more in the sunny season than it does in the rainy season, but it all averages out. Hope that helps!

  10. Anonymous says:

    I sell MTTP charge control that convert excess voltage to need current for you charging.This mitigate the challenge.I also sell and distribute hybrid inverters,batteries and solar panel with warranty in Nigeria.Call me on 07030375697.

  11. Anonymous says:

    I have a question, how many watts does one solar panel produce in one day? On a cloudy day

    1. Ben Zientara says:

      It depends on many factors, especially your location on the planet. In Oregon, a single 200W solar panel will produce an average of about .76 kWh of electricity in a day. In California, that number is more like 1.15 kWh. Again, those are average numbers, so some days will be lower and some higher.

  12. Anonymous says:

    Unfortunately a one-sided article that neglects to mention the cost of the panels. Add the costs into the equation, and the result is drastically different. “Monorail, monorail.” .”

  13. Anonymous says:

    Cloudy days are very significant if the bulk of your grid electricity savings comes from peak power charges. Peak power charges are a major part of institutional electric price structures.

  14. Anonymous says:

    Clouds shrink Amperage 90%, Voltage by 1% according to our tests. http://www.solarscientist.com/solartest.html

  15. Anonymous says:

    my inverter betwen 11 and 1 o clock switches off and green blinks and it will start again but always when its cloudy days most of the time when the sun comes out i have 6 panels and tigo my inverter is 1600 panels 250 watts and 6 panels and tigo

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