Solar panels generate electricity even when the sun isn’t shining brightly. While their output is lower on cloudy days than on days with clear skies, solar panels can still convert diffused sunlight into usable energy. Many modern systems perform efficiently in various conditions, including overcast skies. In this guide, we’ll explain how solar panels work in cloudy weather and how leading solar providers design systems to maintain reliable performance year-round.
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How Solar Panels Work
Solar panels convert 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 best solar batteries can provide power for longer periods of time during outages.
Solar Panels on Cloudy Days
Solar PV panels generate electricity using both direct and indirect sunlight, allowing them to function even when clouds diffuse light. However, they operate most efficiently under full sun exposure. The decrease in solar power output on cloudy days depends on factors such as panel efficiency, placement, and the extent of cloud cover.
If your solar panels aren’t producing enough energy during cloudy conditions, your home can still receive power. Fully off-grid systems rely on backup storage, such as a solar battery option or generator. However, most residential solar systems are grid-tied, meaning they automatically draw power from the utility grid when needed.
Other Weather Conditions That Impact Solar Panel Efficiency
In addition to cloudy days, other weather conditions can affect how much energy your solar panels produce. Learn more:
- Heat and humidity: High temperatures can reduce solar panel output or efficiency. Solar panel efficiency typically drops by about 0.5% for every degree above 25 degrees Celsius (77 degrees Fahrenheit), according to solar system installers. High humidity often leads to increased cloud cover and rainfall, reducing the amount of sunlight reaching the panels.
- Rain: While rainy days reduce sunlight, the water can benefit your system by naturally washing away dust and debris that block light, aiding in solar panel maintenance. However, water droplets on the panel surface can temporarily scatter light and reduce absorption.
- Snow: Light snow shouldn’t impact panel performance. Typically, the wind will blow it off, and sunlight can still filter through. Heavy snow accumulation, however, can completely block panels from receiving light, halting energy production until the snow melts or is removed.
- Wind: Wind helps cool panels during hot weather, improving efficiency by lowering surface temperatures. However, extreme winds can pose a physical threat, potentially damaging roof mounts or panel racking if not properly secured.
Storing Solar Power for Cloudy Days
When designing your system, professional solar installers consider historical weather patterns and your daily energy usage. They may recommend high-efficiency solar panels or a battery storage system to maintain sufficient power on cloudy days. They can also help determine the best angle, number of panels, and placement to maximize performance.
Homeowners can store surplus electricity using a solar storage system. Energy storage isn’t 100% efficient, but it 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 the retail price for the electricity you feed back into the grid. Excess energy generated on sunny days can offset the cost of grid electricity used during low-production periods. Most states require net metering by law, but state policies vary widely.
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 panels. 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.
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.
