Solar panels absorb energy from the sun and convert it into usable power for the home. But do solar panels work on cloudy days? The answer is yes—although your solar panel system will be most efficient in direct sunlight, it can still generate electricity in gloomy weather. In this guide, we’ll delve into the science behind solar power and how weather conditions affect solar panel efficiency.

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How Solar Panels Work

Solar technology converts sunlight into electrical energy using photovoltaic (PV) cells made of semiconductor material. When the sun’s rays hit the panels, the solar PV cells absorb photons, causing the electrons in the semiconductor material to dislodge and flow. This movement of electrons produces direct current (DC) electricity, which an inverter converts into alternating current (AC) electricity for use in the home.

If there’s excess energy, you can store it using solar batteries or send it back to the electric grid for potential credits. Saving solar energy is useful on rainy days or during power outages and can even allow you to live comfortably off-grid. The most powerful solar batteries can provide power for longer periods of time during outages.

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Solar Panels on Cloudy Days

Solar PV panels can use either direct or indirect sunlight to generate power, so they still work when light is reflected or partially blocked by clouds. However, panels are more effective when there’s full sun.

The reduction in solar power depends on the efficiency and placement of the solar panels and the percentage of cloud coverage. According to the Environmental and Energy Study Institute (EESI), the solar panels on your home still operate at 80% of their maximum output during partly cloudy weather, but this number decreases on overcast days.

If your solar panels aren’t producing enough energy on cloudy days, don’t worry—you still have options. Unless you have a fully off-grid solar system, it will probably draw power from the grid automatically when needed. In areas where net metering is available, the cost may even be offset by the extra energy your system fed back into the grid on sunny days.

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Other Weather Conditions that Impact Solar Panel Efficiency

Other weather conditions can impact your energy solar panel, including the following:

• Heat and humidity: Higher temperatures and humidity reduce the amount of power solar panels produce. Humidity creates a layer of water on the panel’s surface, which can decrease total power production efficiency by 10%–20%.
• Rain: Rain can have an impact on how solar panels absorb sunlight. It can help keep your panels operating efficiently by washing away dirt and debris, but studies show that water droplets on the panel’s surface can potentially reduce its performance.
• Snow: A light dusting of snow has minimal impact on solar panel efficiency. The wind can easily blow off light snow, and light may still filter through. Heavy snow accumulation prevents the PV panels from absorbing light and generating power.
• Wind: Wind has little impact on solar panel efficiency unless there’s extreme heat. Solar cells work best at low temperatures, and studies show that wind can reduce PV panel temperatures and improve electrical production.

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Storing Solar Power for Cloudy Days

When designing your system, professional solar installers will consider historical weather patterns and your daily energy usage. They may recommend high-efficiency solar panels or a solar battery system to ensure that your system provides enough power even on cloudy days.

Homeowners can store surplus electricity using a solar storage system. Energy storage isn’t 100% efficient but allows for the flexible use of energy, such as at nighttime or on overcast days, so you don’t have to rely on backup power from the grid.

Another option is to send extra electricity to the power grid, called net metering. With this system, your power provider pays you retail price for the electricity you feed back into the grid. Most states require net metering by law, but state policies vary widely.

To learn more about installing a solar storage system, check out the video below with plumbing and heating expert Richard Trethewey:

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Our Conclusion

Solar panels will continue to generate power even on the cloudiest of days. However, direct sunlight is optimal, and an overcast sky will reduce the output of your solar system. A solar battery can help you save extra energy on days when there’s less sunlight, or you may be able send it to the grid and receive credit from the utility company for the energy you generate. For more information, read our guide to the basics of solar panels.

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FAQ About Solar Panels on Cloudy Days

How efficient is a solar panel on a cloudy day?

Solar panels are less efficient on cloudy days, but they still produce electricity. Depending on how thick the cloud cover is, a solar panel might only produce 10–25% of its normal output on a cloudy day.

How do solar panels work when there is no sun?

Solar panels need at least a little sunlight to work, but it doesn’t have to be direct sunlight. They can also use the indirect sunlight available on cloudy days. However, they do not work at night, when there is no sun.

Do solar panels work with moonlight?

No, solar panels do not work with moonlight. Although moonlight is reflected sunlight, the intensity is far too weak for your solar panels to work at night.

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