How cloudy & cold days affect solar production

Anne BrockOur Town Outdoors

Mid-summer allows us to soak up the longest days of the year in the Northern Hemisphere, favoring pool time and garden growth. It also provides plenty of sunshine in general to support solar power production at your home or business. Yet, cooler, cloudier days may not always be the summer party-crashers you think they are for your solar system. Here’s why:

Solar modules work by absorbing energy from the sun’s light, but not its heat. So, while clear, sunny days will typically produce a lot of electricity via your photovoltaic system, it need not be the hottest day of the year to work. Instead, peak performance comes on sunny but cooler days. This makes it possible for solar production in the clearest days of winter, or for better performance when a breeze cools things on a summer afternoon.

Clouds can curb solar production, but not necessarily stop it. Thinner clouds are more likely to let sunlight filter through and a continuation of energy production. Thicker clouds on extremely overcast days may not. A solar module may be producing a fraction of its typical amount on a cloudy day. Planning for solar means looking at year-around weather data for your location, so you can anticipate those cloudy days.

How are some solar system owners planning for less-sunny scenarios? Some are choosing battery storage to transfer extra electricity from the highest producing days to the lower producing ones. Some are choosing backup generators for an alternative source of power that gives added assurance they can keep the HVAC and lights on during an outage.

Before you install solar, get a year-around look at sun, clouds and rain chances where you are, so you can estimate accordingly. The government offers a free site where you can get a rough estimate of this for yourself.

Anne Brock is marketing coordinator for Solar Alliance. She can be reached at: 865-221-8349 or


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