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July 1, 2015

When a fan spins and nobody is there, is it cooling?

Fans cool people. Fans don’t significantly cool rooms, furniture, or walls.

Moving air cools us by removing our body heat from our skin (think wind chill). This process is enhanced through the evaporation of sweat from our skin.

There are only two times that fans can actually cool a room:

• Removing excess heat and moisture through bathroom or kitchen fans.
• Moving cooler air into a room, either through an air conditioning system or by moving cooler outside air into the house.

The bottom line: A turning fan in an unoccupied space is doing one thing—using electricity.

Fans are effective home cooling devices for rooms—when occupied. Just as with wind chill in the winter, moving air will quickly reduce our skin temperature, especially when evaporating perspiration. Even homes that use air conditioning can benefit from the use of fans. Cooling our bodies with a fan means we can turn up the temperature on our air conditioner, and save energy overall.

For instance, a ceiling fan will allow you to raise the thermostat setting about 4 degrees with no reduction in comfort, according to the U.S. Department of Energy (DOE). During moderately hot weather, ceiling fans may allow you to avoid using your air conditioner altogether. When shopping for ceiling fans, look for the ENERGY STAR® label. This designation means the fans will move air 20 percent more efficiently, on average, than standard models.

During Minnesota’s winter months, fans will not reduce your heating costs, because the movement of air currents will cool our bodies slightly. This cooling effect may prompt residents to unnecessarily raise their thermostat and overheat their homes.

For more information on fans, visit the Minnesota Department of Commerce Home Energy Guide and the DOE’s “Fans for Cooling” webpage.

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Minnesota Energy Tips is provided twice a month by the Minnesota Department of Commerce, Division of Energy Resources. Contact the division’s Energy Information Center at energy.info@state.mn.us or 800-657-3710 with energy questions.