Green Lifestyle

Published on August 20th, 2020 | by Scott Cooney


Weird trick cuts electric bill and makes your fans cool you better

It’s hot out, amiright? Death Valley just registered the hottest temp ever recorded in planet earth’s history. Thanks to the fossil fuel industry’s propaganda around climate change and puppet politicians like Donald Trump, we’re quickly turning into Venus, the balmy 800 degree “paradise” one planet closer to the sun.

So if you’re like me and don’t have AC in your home, you’re probably, like me, using a fan to help keep yourself cool during these dog days of summer. That’s good – fans are much more energy efficient than AC units, and get the job done, if used right. There’s an interesting little trick with fans, though, that few people know. This trick will not only keep you cooler, it will also cut how much electricity your fan is using, meaning less spending on your utility bills.

To understand the trick, here’s a thermal image of a room with a ceiling fan. Thermal images are basically pictures of heat. Red/orange indicates heat, whereas blue/purple colors show where things are cooler. In the picture below, you can see that the wall on the left is hot. I took this photo on a day in which the sun was setting off to the left side, to demonstrate just how hot the walls of the house can get, to encourage the homeowner to think about tree planting and shading as a way to cool their home substantially.

However, check out the fan. The motor inside the fan is burning hot–so much so that it matches the hottest part of the wall facing a blazing sunset in the summer in the tropics. We’ll come back to that in a second.

The second key thing to remember about fans is that they work through convection. As air moves over your skin, it evaporates perspiration (sweat), and as it evaporates, it draws heat away from your body. Other than that, there is no “conditioning” of the air. Fans don’t “cool” the air, they just move it. So this is element two – fans cool by the wind chill effect, more or less.

Add these two things up. First, fan motors generate heat. Second, fans work to cool us only by direct wind chill. So unless you are there to feel the wind chill, fans actually heat up the room. Many people believe that fans help cool rooms. The truth is that they actually heat the room.

So the trick? Just like lights, turn ’em off when you leave the room. Given that fans can use 80-120 watts, it’ll save you a lot of money, reduce carbon pollution, and actually keep your place cooler. When you get home, or re-enter the room? Just flip the fan back on.

So just remember: fans cool people, not rooms. 

Check out these other tips to stay cool without expensive AC. 

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About the Author

Scott Cooney (twitter: scottcooney) is an adjunct professor of Sustainability in the MBA program at the University of Hawai'i, green business startup coach, author of Build a Green Small Business: Profitable Ways to Become an Ecopreneur (McGraw-Hill), and developer of the sustainability board game GBO Hawai'i. Scott has started, grown and sold two mission-driven businesses, failed miserably at a third, and is currently in his fourth. Scott's current company has three divisions: a sustainability blog network that includes the world's biggest clean energy website and reached over 5 million readers in December 2013 alone; Pono Home, a turnkey and franchiseable green home consulting service that won entrance into the clean tech incubator known as Energy Excelerator; and Cost of Solar, a solar lead generation service to connect interested homeowners and solar contractors. In his spare time, Scott surfs, plays ultimate frisbee and enjoys a good, long bike ride. Find Scott on

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