Just about every window air conditioner that comes into the Good Housekeeping Home Improvement & Outdoor Lab for testing features a digital display, rather than the old-fashioned manual dials. Along with the power button, temperature control, and fan speeds, most displays also have a timer feature that allows you to program the AC to turn on or off after a set period.
The timer is marketed as an energy-saving feature, since it allows you to limit your AC use, for example, by programming the unit to turn off a few hours after you go to bed, so it’s not running all night. Or you can set the AC to turn on an hour before you get home from work, instead of leaving it on all day.
That makes sense in theory. But in most situations, turning the AC on and off throughout the day ends up using more energy, since the machine will have to work harder to bring the temperature back down to a comfortable level. On top of the energy loss, turning the AC off during a summer heat wave can drive up indoor humidity levels, to the point where mold and mildew start to thrive.
This is why I generally advise against using the timer. Instead, get familiar with the Energy Saving Mode, another feature that’s common on modern ACs. Also referred to as Eco Mode (short for “economy”), this setting allows the compressor to run at slower speeds throughout the day, depending on the conditions in the room. It’s especially useful for nighttime cooling or when you’re away from home, when it can reduce electricity consumption by up to 30%.
Even if you’re heading out of town for the weekend, my advice is to leave the AC running in Energy Saving Mode, though at a higher temperature, say between 80°F and 85°F. That will keep the place cool and dry enough that you won’t come home to mushrooms growing in the bathroom, while also preventing your electric bill from soaring.
Having written thousands of product reviews and how-to articles on all aspects of home ownership, from routine maintenance to major renovations, Dan (he/him) brings more than 20 years of industry experience to his role as the director of the Home Improvement & Outdoor Lab at the Good Housekeeping Institute. A one-time roofer and a serial remodeler, Dan can often be found keeping house at his restored Brooklyn brownstone, where he lives with his wife and kids.
