Do Solar Panels Still Work on Cloudy Days?

Do Solar Panels Still Work on Cloudy Days?

Published 9/20/2023

At Sunrun, we install a lot of solar and battery systems. And one of the most common questions we get is, "Will the panels work if it's cloudy?" Here's the good news— full sun days are not a requirement for solar power generation. Solar panels can still produce electricity even when the weather is cloudy and gray.

If you’re considering going solar, don’t let your local weather deter you.

Read on to learn exactly how solar panels work on cloudy days and why solar can still be a smart investment, even if you don't reside in sunny California.

How do solar panels actually work?

Before we dive into solar performance on cloudy days, let’s do a quick refresher on how solar panels work in general.

Solar panels generate electricity through the photovoltaic effect. 

Each solar cell contains a semiconductor material, usually silicon. When sunlight hits the solar cell, photons from the light knock electrons loose from their atoms. This generates a flow of electricity.

An individual solar cell only produces a small amount of energy. But when cells are connected together in a panel, they can generate enough electricity to power your home.

The electricity generated flows from the solar panels into an inverter. The inverter converts the DC power into alternating current (AC), which is used to power your home.

Any excess electricity that isn’t immediately used is stored in a battery or fed back into the utility grid. Net metering programs provide credits for the energy fed back to the utility to offset your electricity usage at night or on cloudy stretches.

That covers the basic solar panel operation. Now let’s look at how panels perform when the skies are overcast.

Do solar panels produce energy on cloudy days?

Yes, solar panels can still generate electricity even on cloudy and rainy days! The key reason is that solar cells can absorb both direct and diffuse sunlight.

Direct sunlight is the unobstructed beams that shine down when the sky is clear. Diffuse sunlight is sunlight that has been scattered in the atmosphere by clouds, haze, dust, etc.

On overcast days, solar panels are still exposed to ambient diffuse light. While less intense than direct sunlight, this diffuse light can still excite electrons in the solar cells and produce an electrical current.

So don’t believe the myth that solar panels are useless on cloudy days. While they produce less power compared to the full sun, they can still generate electricity from that diffuse light.

How much do clouds impact solar panel efficiency?

The amount of solar electricity you can expect your home to generate during a cloudy day will vary due to:

  • Thickness of cloud cover - Thinner, higher clouds allow more light through compared to thick, low-lying storm clouds

  • Type of cloud - High-wispy cirrus clouds permit more sunlight than dense cumulus clouds. Stratus clouds fall somewhere in between

  • Time of year - More daylight hours in summer vs. winter means more total energy production

  • Geographic location - Southern regions of the country receive more annual sunlight than northern areas

  • Local weather patterns - Some areas simply have more overcast days than others

Understanding these factors can give you realistic expectations for solar output. But keep in mind that if you choose to go solar with an experienced partner like Sunrun, you’ll be sure to get a solar system that can accommodate your energy needs even with varying weather factored in.

That said, here are some typical solar panel efficiencies based on sky conditions:

  • Clear, sunny day - 100% efficiency1

  • Partly cloudy day - 50-80% efficiency1

  • Heavily overcast day - 10-25% efficiency1

Common myths about solar panels on cloudy days

Let’s clear up some common misconceptions about solar and cloudy weather:

Myth: Solar panels don’t work at all on cloudy days.

Fact: Solar panels still generate electricity from diffuse light on overcast and rainy days, just at reduced efficiency.

Myth: Cloudy weather makes solar power unreliable.

Fact: Advanced forecasting and grid integration techniques help balance solar supply and demand, even on cloudy days.

Myth: Solar only works well in the sunniest locations.

Fact: Modern solar panels can still provide clean energy and savings in locations with average sunlight levels. Proper solar panel orientation and tilt help maximize production.

The truth is that most locations receive enough annual sunlight for solar panels to be worthwhile.

To make sure your solar setup can handle the ups and downs of your local weather and keep your energy needs covered, teaming up with a trusted solar provider like Sunrun is a smart move. We’ll craft a personalized system and offer 24/7 system monitoring for total peace of mind.

Do solar panels work at night?

Solar panels require sunlight to function. At night when it’s dark, solar cells stop generating electricity. So how can solar power your home around the clock?

The answer is solar battery storage. By storing excess solar electricity produced during the daytime, batteries can discharge power at night to keep your lights on after sunset.

Batteries also provide backup power during prolonged overcast periods and weather emergencies. Adding battery storage provides true energy independence and resilience.

Solar battery storage systems capture extra solar electricity produced during sunny weather and save it for later use. 

With sufficient battery storage, your solar system can keep the lights on and appliances running even when the panels aren’t actively producing power.

Should you go solar if you’re in a cloudy climate?

If you live in an area with lots of rainy and overcast days, you may be wondering if solar power is still a smart investment.

The answer is often yes—with the right solar system design, even cloudy locations can benefit from solar energy.

Here are a few tips to maximize solar production in low-sunlight areas:

  • Size your solar array 25-35% larger to account for lower yields

  • Add more panels on north-facing roofs to capture diffuse light

  • Use high-efficiency panel models with higher wattage

  • Install east/west facing panels to catch morning and afternoon sun

  • Add solar battery storage to save surplus power for cloudy periods

No matter where you live, there are ways to optimize solar generation. Get a quote with Sunrun to understand how much you could save by going solar. 

When do solar panels produce the most energy?

Solar panels work whenever sunlight is available but produce the most electricity during peak sun hours:

  • Spring - Longer days and more direct sunlight after winter

  • Summer - Maximum daylight hours around the solstice

  • Fall - Still fairly long days before winter

  • Winter - Shortest days but solar output boosted by reflective snow

The most power is generated when the sun is high overhead. Solar production peaks in the late morning and early afternoon.

South-facing panels tilted at an optimal angle receive the most direct sun exposure. But even on cloudy days, ambient and reflected light keeps solar panels generating energy.

Other Frequently Asked Questions (FAQs)

Should I install solar if I live in a cloudy climate?

  • Yes, solar can still be a cost-effective investment, even in cloudier climates

  • Properly sizing the system and optimizing the panel orientation can help maximize solar production during suboptimal weather

How much less efficient are my solar panels on cloudy days or at night?

  • Solar panels produce no electricity at night without sunlight.

  • On very overcast days, a solar array's efficiency may drop to 10-25% of its peak capacity, according to NREL data.

  • On partly cloudy days, efficiency ranges from 50-80% 

How much electricity do solar panels produce on overcast days?

  • Production levels depend on cloud thickness, type, and location

  • High-efficiency panels will generate more electricity on cloudy days

Can solar panels work efficiently in rainy climates?

  • Yes, solar can still be effective in rainy climates with proper system sizing and orientation

  • Rain can help clean dust off panels, potentially boosting efficiency

  • Adding batteries stores surplus solar energy for use when needed

How does weather impact solar panel efficiency?

  • Cloud cover, rain, snow, and pollution affect how much sunlight reaches panels

  • Cold weather can slightly reduce solar cell efficiency

  • Solar efficiency drops in winter with fewer daylight hours

What factors maximize solar production on cloudy days?

  • High-efficiency solar panels

  • Proper orientation and tilt

  • Keeping panels clean and clear of obstructions

How can I use solar power at night?

  • Adding solar batteries stores surplus daytime energy for nighttime use

  • Grid-connected systems can pull electricity from the utility at night

  • Standalone off-grid systems require batteries or generators

Bottom line: When does solar work best?

While solar efficiency may drop on cloudy days, panels can still generate meaningful amounts of electricity from diffuse ambient light.

With proper system sizing and orientation, solar power can be a smart investment even in overcast climates.

Your solar panels will produce the most energy during peak daylight hours with direct sun exposure, but they can still offset a significant portion of your electricity usage on cloudy days. And adding solar batteries to your installation ensures you’ll have power even during unexpected weather conditions.

Consider switching to solar

Don’t let your local weather be a dealbreaker. Our expert Solar Advisors guide you through the complexities and details of solar—from understanding your energy bills, to installation and more. And each Sunrun solar system is custom-designed to fit your home’s unique needs so you can harness the power of the sun, rain or shine.

As the nation's #1 home solar & battery installer, we provide dedicated support from initial system design to powering on your system. Our personalized approach ensures that you make the right decisions for your home solar system.


1. Best Research-Cell Efficiency Chart ┃ NREL

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