How Do Solar Panels Work in Winter?

Misconceptions

The use of solar panels to tap the sun's energy for electric power has long been popular in areas of the United States that have substantial amounts of sun and warmth throughout the year, such as Florida or southern California. In many areas that face severe winter weather each year, however, the idea persists that solar panels are ineffective during the winter months. This is not the case. While the amount of sunlight present does determine the amount of energy collected, low temperature has no effect on the panels' operation; in fact, their electronics function better in the cold than on very hot days. Solar energy can still be effectively caught in winter as long as a modest degree of maintenance is done on the panels.

Overcast Conditions

Solar panels gather the maximum amount of energy under sunny conditions in the peak afternoon hours. Nevertheless, they are able to gather some amount of light even at night from moonlight, starlight and city or street lights. In cities such as Seattle or Cleveland, where the winter skies are consistently overcast, solar panels still receive from 5 to 50 percent of summertime radiation during the daytime depending on the thickness of the cloud layer. This is enough to contribute significantly to household needs for electricity if the panels have been oriented correctly to point toward the winter sun.

Remove Snow From Panels

Anything that diminishes the amount of light penetrating the solar panels--whether it is dirt, leaves, bird droppings or tree pollen--reduces the amount of energy collected. For this reason, regular cleaning of the panels is recommended in all seasons to keep panels operating at peak efficiency. But the most dramatic drop in collection occurs after a snowfall. If snow totals are low to moderate and the day's high temperature is expected to reach or exceed 32 degrees, solar panels will warm up quickly and melt the snow. If several inches of snow fall with persistently cold conditions, however, the snow must be cleaned off the panels for them to collect any solar radiation. The easiest way to do this is to specially modify a "snow rake" (available in hardware stores) by affixing a squeegee-type blade to the sweeping edge. The long-handled rake allows convenient access to first-floor roofs, and the rubber strip on the edge will prevent scratching or damaging the surface of the solar panels. It is extremely dangerous to climb onto roofs in snowy or icy conditions, and snow on any second-floor solar panels will simply have to be left there, but clearing it from just the lower accessible panels will significantly increase the amount of sunlight collected.

Resources

• Orienting solar panels for winter