Solar Panels Do Work On Cloudy Days

February 8th, 2018 by Jake Richardson

This article is part of our “CleanTechnica Answer Box” collection. In this collection of articles, we respond to dozens of common anti-cleantech myths.

Myth: solar panels don’t work when it’s cloudy.

Short answer: Solar panels do produce electricity in cloudy weather. They don’t produce as much electricity as they do on sunny days, but they have been shown to produce 25% of what they produce on a sunny day, or 10% when it’s very cloudy.

Some critics of solar power say that solar panels don’t produce electricity on cloudy days. This claim is false. Solar panels can still can produce 10–25% of their typical output on a cloudy day. Obviously, this amount is much less than during periods of direct sunlight, but it is not nothing.

We may assume that solar panels thrive in hot, sunny weather, but too much heat can actually reduce solar panel output 10–25%. So, very hot weather isn’t the best condition for them. “The problem is, most solar panels’ power outputs start to degrade if the temperature of the panel goes over about 25°C. This is why, if you look at the specification label on a solar panel, most manufacturers quote the solar power output at a panel temperature of 25degC.”

This is why a solar power system might be more effective in San Francisco than in much hotter Las Vegas, even though Vegas has more sunny days. San Francisco is well known for its foggy days with cool weather, so it might be easy to assume that solar power wouldn’t do well there. However, rooftop solar power systems in San Francisco do function well. The amount of direct sunlight is reduced by fog and clouds, but solar panels function better at cooler temperatures, so the electricity output in San Francisco is still significant. Using a home solar power system there can save approximately $1,500 per year on utility bills, according to an analysis conducted by SolarCity.

You can also save $1,500 with solar power in Boston. Even though this city has such cold winters and cool temperatures in fall, solar power works well there and can considerably cut electricity bills.

One of the American cities with the most cloudy days is Seattle, but solar power is continuing to grow there as well. “Seattle is quickly becoming one of the best cities for solar in America thanks to Washington’s great payback incentive and net-metering policy as well as the city of Seattle’s growing market competition.”

Another one of the cloudiest cities, Portland, is also a leader among American cities in solar power — the 17th best US city in terms of solar capacity.

If you live in an area with cloudy, cool weather, you can still purchase and benefit from a solar power system, and don’t let any naysayers tell you otherwise. Sunshine is just part of the story. One major factor to consider if you are looking into buying a solar power system is the cost of electricity from your utility. If it is high or very high, of course, you may be motivated to find an alternative source of electricity, even if your region has cloudy days.



There are also two trends working in favor of solar power in cloudy places: One is that solar panels have gradually become more efficient, especially in cloudy locations. The other is that solar prices have decreased steadily, so it is more affordable to get a larger system for places with less direct sunlight.

Images by skeeze and Alice Donovan Rouse











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