Thursday, March 12, 2020

Drying laundry efficiently: air dry is best, but in a dryer long and cooler is more efficient than short and hot.

A friend asked a question about energy use in clothes dryers.

The discussion started with the understanding that if you can hang your clothes in the breeze on a clothesline, youʻve found the most energy efficient way to dry your laundry.

But if you need to use a dryer, she asked, is more energy efficient to run the dryer longer at a cool temperature, or shorter at a higher temperature.

There are all sorts of variables in this calculation. Different types of fabric. Different starting moisture levels. The more-dry setting (uses more energy) compared to the less dry setting (more efficient.) Gas dryers with electric motors (more energy efficient) versus all-electric dryers (less efficient.) And within those categories, newer dryers that emphasize efficiency versus ones that donʻt.

But given equivalent conditions, and assuming all-electric, it looks like running a dryer longer at a slightly cooler temperature saves energy compared to running it hotter shorter.

Thatʻs because the heating requires so very much more electricity than the motor.

This paper from the American Council for an Energy-Efficient Economy (ACEEE) found that energy savings are available from "using a lower heat setting to reduce the energy spent heating air, cloth, and metal. The clothes get just as dry, though drying time may be longer."

Thereʻs a lot more in that paper, so if youʻre interested, read through it, or at least read the recommendations and conclusions in the last four pages.

And this piece of research is old, but it was authoritatively done by the Oak Ridge National Laboratory, and it also found that itʻs the heating that uses most of the power in a dryer. The dryers back then were not all that different than those today, and ORNL calculated that 91 percent of the energy was used for heating, and 9 percent for all the dryerʻs other functions: tumbling, blowing and running the controls.

The U.S. Governmentʻs website comes to the same conclusion: "Use lower heat settings in the dryer. Even if the drying cycle is longer, you’ll use less energy and be less likely to over-dry your clothes."

The site also has lots of other tips on saving energy in the laundry arena.

© Jan TenBruggencate 2020


Anonymous said...

Been wondering this for a long time; glad to finally have a definitive answer!

Anonymous said...

Been wondering this for a long time; glad to finally have a definitive answer!