Leaving your ceiling fan on when you’re away won’t cool your home

This summer, much of the U.S. has experienced heat waves pushing temperatures above 90 degrees Fahrenheit, and even into the triple digits in a few places. That’s prompting many people to ask about how they can keep themselves and their homes cool without pushing their electricity bill too high. 

One VERIFY reader texted us to ask if they should keep their ceiling fans on even when they’re gone.

THE QUESTION

Can you cool a room by leaving a ceiling fan on while you’re away from home?

THE SOURCES

• University of Florida IFAS Extension, a science resource which includes research about family and consumer sciences

• The Home Depot

• Energy Vanguard, a firm that trains and consults companies on building performance

• North Carolina Advanced Energy Corporation, a nonprofit energy consulting firm

• U.S. Department of Energy

THE ANSWER

No, you cannot cool a room by leaving a ceiling fan on while you’re away from home.

WHAT WE FOUND

Ceiling fans do not actually lower the temperature of a room, says the University of Florida IFAS Extension, a science resource which includes research about family and consumer sciences.

Instead of lowering the room’s air temperature, ceiling fans operate by moving air which makes people feel cooler and more comfortable, says the Home Depot. 

Your body cools itself off through the evaporation of sweat, says Energy Vanguard, a firm that trains and consults companies on building performance. The evaporation accelerates when air moves over your skin, according to North Carolina Advanced Energy Corporation, a nonprofit energy consulting firm. 

Moving air also carries heat away from your body in a process called convection, Energy Vanguard explains. So a fan helps cool your body through evaporation and convection at the same time.

All of our sources say that a fan only benefits you when you’re actually in the room and the air the fan moves can actually travel over your skin. Other living things, such as pets, can also feel cooler when a fan is running.

If you turn on an effective ceiling fan, you can raise your thermostat by about 4 degrees Fahrenheit and feel just as comfortable as you did before, the U.S. Department of Energy (DOE) says. In more temperate places, you might even be able to avoid using your A/C altogether, the DOE says.

But the DOE adds that you should “be certain to turn off ceiling fans when you leave a room.”

Not only does a running ceiling fan fail to cool you or your home when no one’s in the room, it also might actually increase the heat of a room somewhat if you run it too long. The reason is because ceiling fans operate with a motor, and motors release heat when they run, Energy Vanguard says

When you are in the room and running your fan, you’ll want to make sure it’s spinning counterclockwise if you want to feel cooler. A ceiling fan spinning clockwise might end up making the room feel warmer.