What Temperature to Set Air Conditioner in Summer

Summer is quickly approaching, and that means high temperatures and even higher electric bills. In fact, according to a recent study, average electric costs for June through September are expected to reach $719 this year. That’s up from $476 for the same four-month period a decade ago.

It’s enough to give cash-strapped households pause the next time they go to flip on the air conditioner. But would keeping the unit off when you’re not home actually reduce your bill? The answer is probably not.

In milder climates, turning off the A/C for a few hours a day could save some energy and cash. But it depends on lots of factors, including the size and efficiency of your A/C unit, your home’s insulation, local humidity levels, your square footage and how well your HVAC system has been maintained and cared for.

For most people, though, “It doesn’t save money,” says Brad Gall, owner and founder of BG Electrical & Air Conditioning in Brisbane, Australia. “By turning it off, you’re making your A/C go full-throttle every single time it’s turned on, and that gobbles up much more electricity than just maintaining the desired temperature.”

For most households, a strategy called “temperature setbacks” is the most effective way to cut costs, pros say. Here’s what to know about this method and how it could help your A/C bill this summer.

Turning off vs. lowering your A/C

When you turn off your A/C completely for a large portion of the day—particularly in hot weather—your home’s temperature increases quickly, forcing your unit to work harder once you turn it back on.

“The contents of the room—like furnishings and walls—can hold on to residual heat, and A/Cs have to work extra hard to get the room back to the desired temperature once you return,” says Max Veggeberg, CEO of home services company Tetra in Newton, Mass. This strategy’s only smart if you’re leaving home for five-plus days, such as on a vacation, he says.

Strategic temperature setbacks are a better option for day-to-day usage. This involves increasing your home’s temperature by a few degrees Fahrenheit when you’re not around—during work or school, for most people—and turning it back to a more comfortable temperature just before you return home.

“It’s much better to just set the temperature up a notch or two while you’re away and then tune it down again when you’re back,” Gall says. The opposite applies in colder weather. Set the temperature lower—closer to the outside temperature—to ease the load on your system.

Using setbacks also helps you avoid paying peak electricity rates for too long. (Many utility companies charge higher rates during after-work hours—usually from 4 p.m. or 5 p.m. until 8 p.m. or 9 p.m.)

“If you’re coming home after work and cranking up the A/C, there’s a good chance you will wipe out any savings you might have accrued by keeping the unit off all day,” says Shawn McLaughlin, CEO of Emporia, a Littleton, Colo.-company that offers home energy management products.

How to maximize your savings

Keeping your temperature just degree Fahrenheit warmer consistently could save you about 3% on your monthly energy costs, data shows. For a 10% savings, the Energy Department says to shoot for a seven to 10 degree increase for eight hours each day. This strategy can result in more savings if you’re in a milder climate, where temperatures or humidity aren’t too extreme.

“In hot and humid climates, the savings might be less significant due to the high energy required to dehumidify the air,” says Calgary, Alberta-based Asif Bux, owner of HVAC, plumbing and electrical company Comfort Union.

While you can do temperature setbacks manually, a smart thermostat can make it easier, allowing you to set a specific cooling schedule for each day of the week. On work days, you can set the temperature a few degrees higher when you usually leave the house, and then have it start cooling down to your ideal temperature 30 minutes before you return. If you don’t have an ideal temperature, the DOE recommends using a baseline of 78 degrees when at home for the most savings. (Though Gall says most people are comfortable at around 75.) If that’s still too warm for you, keep your ceiling fans on, and make sure they’re running counterclockwise. This ensures cooler air gets pushed downward.

You can also help boost energy savings by changing your HVAC filters regularly, having your system tuned up at least once annually and clearing the unit and coils of any buildup. On indoor units, this might mean dust or pet hair. Outside, you’ll need to brush away grass clippings, leaves and other debris.

“Dirty coils can impede heat transfer, and dirty filters can slow air flow, causing your A/C to work harder for the same output,” Veggeberg says. “In the short term, this can cause higher energy bills. In the long term, it can lead to potential breakdown of your unit.”

Other ways to reduce your energy spend this summer

Fine-tuning your A/C use isn’t the only way to reduce energy use and spending during the summer. Sealing gaps around windows or doors—where cool air can easily escape—can help, as can improving your home’s insulation.

You can also keep inside doors open to allow for better circulation, and make sure your blinds and curtains are closed. Blackout curtains, which help block out UV rays, can keep your home cool, too.

Finally, shift some of your electrical activity from peak hours to lower-use periods when electricity rates are lower—typically anytime before 1 p.m. local time. Run your laundry or dishwasher in the morning, or charge your electric vehicle while you sleep, rather than right when you get home.

“Be aware of time-of-use pricing in your utility area,” McLaughlin says. “Utilities can charge three to four times the standard rate for energy used during certain peak hours.”