Solar Energy Production on Cloudy and Snowy days.

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Photovoltaic solar panels will produce energy on cloudy days. Although it might seem counter-intuitive, consider that solar panels on a rooftop in foggy San Francisco produce nearly the same as the ones in nearby sunny Sacramento. Consider too that Germany (with a climate not that different from Vancouver Canada) leads the world in residential solar right now, and it is generally an overcast climate.   

Montana is a great state for Solar.  Solar electric systems have been installed and working in Montana for over thirty-plus years.  Net-metering allows Montanans to harness the sunshine generated on our long solar days in the summer time, feed back into the utility grid and use the power during our shorter winter days.  Solar irradiation levels vary across the United States, but every state receives enough sunlight to make solar a good investment. Solar can work in almost any climate, as long as panels are properly installed in an un-shaded location. Solar panels work with light, not heat so it doesn’t matter how cold it gets outside. In fact, solar panels perform better in cooler temperatures than extremely hot temperatures.

Solar panels will continue to produce a significant amount of energy even on overcast days. On a cloudy day a solar array can producing 50% or more of its potential, and what’s even more exciting, those lovely days when the big poofy clouds are passing by, something called cloud edge effect is occurring. Cloud edge effect can actually increase your array’s production. Just like light through a magnifying glass, cloud edge effect amplifies the sun’s rays as they hit your solar array, sending more watts through your system then you might otherwise expect!

Finally,  what happens when solar panels are snowed in?  As we have said, in Western Montana, grid-tie, net-metered homes make a majority of their solar power in the summer months.  Winter power generation is a bonus, rather than a necessity.  The days are shorter, the sun is lower and the sky is often overcast.  This does not mean that we don’t generate any power, it just means that we generate significantly less in the months around winter solstice. Our sizing programs illustrate this well.  December sunlight in Missoula Montana is summarized as 1.7 equivalent average sun hours while July data shows 7.5 average hours.  So relax.  Modules are generally set at an angle that enough snow will begin to shed, temperatures permitting.  The cells are of dark colors that promote melting and with enough consecutive sunny days your modules will be generating power once again.

Fun Facts:  On NorthWestern Energy net-metered homes, energy production and usage are reset annually April 1st.  So your solar electric photovoltaic system generates power in July (running your meter backwards) and you can use that generated credit now when your modules and you are snowed in.

If you enjoyed this blog and have more questions please see our other blogs, site videos and informationals here on Or contact SBS Solar, Inc. for more information at [email protected] or 406-541-8410. This Blog was created, researched, and edited by SBS Solar, Inc. staff and is copyright of SBS Solar, Inc.

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