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Illustration of Vineyard Wind's proposal to construct a wind energy project off the coast of Massachusetts. Vineyward Wind

By Hannah Hunt

Extreme weather events offer an opportunity to take stock of our power system—how well will it withstand days of prolonged stress? Earlier this year, the eastern half of the U.S. faced one of these trials, as the "Bomb Cyclone" blasted the region with frigid air for a number of days.

The result: no major power plant outages, and a power system that held strong in the face of challenging weather conditions. And wind power made an important contribution to a resilient energy mix, helping to keep the lights on for American families and businesses.

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By Greg Alvarez

Last week I predicted it wouldn't be long before we had more news on Fortune 500 wind power purchases. Well, a whole seven days passed before there were new deals to report.

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MAXSHOT / iStock / Getty Images

Solar panels allow you to harness the sun's clean, renewable energy, potentially cutting your electric bills as well as your environmental footprint. But do solar panels work on cloudy days, or during seasons of less-than-optimal sun exposure? For homeowners who live outside of the Sun Belt, this is a critical question to consider before moving ahead with solar panel installation.

In this article, we'll go over how solar panels work on cloudy days, whether solar panels work at night, and how to ensure you always have accessible power — even when your panels aren't producing solar energy.

How Solar Panels Work on Cloudy Days

Photovoltaic (PV) solar panels can use both direct and indirect sunlight to generate electrical power. This means they can still be productive even when there is cloud coverage. With that said, solar panels are most efficient and productive when they are soaking up direct sunlight on sunny days.

While solar panels still work even when the light is reflected or partially obstructed by clouds, their energy production capacity will be diminished. On average, solar panels will generate 10 to 25% of their normal power output on days with heavy cloud coverage.

With clouds usually comes rain, and here's a fact that might surprise you: Rain actually helps solar panels work more effectively. That's because rain washes away any dirt or dust that has gathered on your panels so that they can more efficiently absorb sunlight.

Do Solar Panels Work at Night?

While solar panels can still function on cloudy days, they cannot work at night. The reason for this is simple: Solar panels work because of a scientific principle called the photovoltaic effect, wherein solar cells are activated by sunlight, generating electrical current. Without light, the photovoltaic effect cannot be triggered, and no electric power can be generated.

One way to tell if your panels are still producing energy is to look at public lights. As a general rule of thumb, if street lamps or other lights are turned off — whether on cloudy days or in the evening — your solar panels will be producing energy. If they're illuminated, it's likely too dark out for your solar panel system to work.

Storing Solar Energy to Use on Cloudy Days and at Night

During hours of peak sunlight, your solar panels may actually generate more power than you need. This surplus power can be used to provide extra electricity on cloudy days or at night.

But how do you store this energy for future use? There are a couple of options to consider:

You can store surplus energy in a solar battery.

When you add a solar battery to your residential solar installation, any excess electricity can be collected and used during hours of suboptimal sun exposure, including nighttime hours and during exceptionally cloudy weather.

Batteries may allow you to run your solar PV system all day long, though there are some drawbacks of battery storage to be aware of:

  • It's one more thing you need to install.
  • It adds to the total cost of your solar system.
  • Batteries will take up a bit of space.
  • You will likely need multiple batteries if you want electricity for more than a handful of hours. For example, Tesla solar installations require two Powerwall batteries if your system is over 13 kilowatts.

You can use a net metering program.

Net metering programs enable you to transmit any excess power your system produces into your municipal electric grid, receiving credits from your utility company. Those credits can be cashed in to offset any electrical costs you incur on overcast days or at night when you cannot power your home with solar energy alone.

Net metering can ultimately be a cost-effective option and can significantly lower your electricity bills, but there are a few drawbacks to consider, including:

  • You may not always break even.
  • In some cases, you may still owe some money to your utility provider.
  • Net metering programs are not offered in all areas and by all utility companies.

Is Residential Solar Right for You?

Now that you know solar panels can work even when the sun isn't directly shining and that there are ways to store your energy for times your panels aren't producing electricity, you may be more interested in installing your own system.

You can get started with a free, no-obligation quote from a top solar company in your area by filling out the 30-second form below.

FAQ: Do Solar Panels Work on Cloudy Days?

How efficient are solar panels on cloudy days?

It depends on the panels, but as a rule of thumb, you can expect your solar panels to work at 10 to 25% efficiency on cloudy days.

How do solar panels work when there is no sun?

If there is literally no sunlight (e.g., at night), then solar panels do not work. This is because the photovoltaic effect, which is the process through which panels convert sunlight into energy, requires there to be some light available to convert.

However, you can potentially use surplus solar power that you've stored in a battery. Also note that solar panels can work with indirect light, meaning they can function even when the sun is obscured by cloud coverage.

Do solar panels work on snowy days?

If there is cloud coverage and diminished sunlight, then solar panels will not work at their maximum efficiency level on snowy days. With that said, the snow itself is usually not a problem, particularly because a dusting of snow is easily whisked away by the wind.

Snow will only impede your solar panels if the snowfall is so extreme that the panels become completely buried, or if the weight of the snow compromises the integrity of your solar panel structures.

Will my solar panels generate electricity during cloudy, rainy or snowy days?

Cloudy days may limit your solar panel's efficiency, but you'll still be able to generate some electricity. Rainy days can actually help clean your panels, making them even more effective. And snowy days are only a problem if the snow is so extreme that the panels are totally submerged, without any part of them exposed to the sun.

By John Hensley

Fresh off the first-ever American Wind Week, the Department of Energy (DOE) National Renewable Energy Laboratory (NREL) released a new report finding wind energy cost reductions of 50 percent are possible by 2030. That's on top of the 66 percent cost reduction since 2009.

Envisioning the wind plant of the near-future—a "collection of intelligent and innovative machines operating in a highly coordinated way"—NREL expects advancements in wind turbine design, materials and controls to unlock major performance improvements and cost reductions.

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American Wind Energy Association

Using a new map tool released Thursday, anyone can now easily view the location of every utility-scale wind project and wind-related manufacturing facility in the U.S. With the very first American Wind Week in full swing, the American Wind Energy Association (AWEA) released the map to help people visualize the growth of America's largest source of renewable energy capacity.

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By Greg Alvarez

Ohio lawmakers are currently considering a measure that could transform the state's rural communities, and last week they heard powerful testimony from those who will be directly impacted.

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By Greg Alvarez

The Oklahoman recently took a look at what the Sooner State's growing wind industry has meant for rural school districts.

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America's wind power workforce installed 908 utility-scale turbines in the first quarter of 2017, totaling 2,000 megawatts (MW) of capacity. This is the wind industry's strongest start in eight years, according to a new report released Tuesday by the American Wind Energy Association (AWEA).

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By Greg Alvarez

Over the past few months, we've seen big wind energy investments from the likes of GM, Facebook, Home Depot and others. But one of the world's largest companies and leading proponents of doing business using 100 percent renewable energy, has been conspicuously absent: Apple.

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By John Hensley

AWEA released its U.S. Wind Industry Annual Market Report, Year Ending 2016 today, which showcases strong, steady growth throughout the year.

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Chicago Mayor Rahm Emanuel atop Shedd Aquarium.

By Alexander Laska

The city of Chicago announced this week that renewable energy will power 100 percent of all of its government buildings by 2025, making the Windy City the country's largest to make that pledge.

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By Greg Alvarez, American Wind Energy Association

All of the new wind farms built over the past few years are making an impact: New data from the U.S. Energy Information Administration finds the country generated more than 5.5 percent of its electricity using wind in 2016.

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