Do Solar Panels Work on Cloudy Days? What About at Night?
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 DaysPhotovoltaic (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 NightDuring 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.
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.