Turning AC Off When Not Home: Right or Wrong?

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Updated May 2, 2023

When readying to leave for the day or a long trip, many people question whether they should leave the air conditioner on when not at home. The answer to this depends on what type of air conditioner you own. But there’s good news because the best air conditioners come with settings that allow you to optimize your AC unit for maximum efficiency when away.

If you have a central AC unit, the answer to this question is that you should seldom fully turn your unit off — even when going on long trips. This conclusion is because, while it always costs to run the AC, it often uses much more energy to bring a central AC up to the correct temperature. Other elements that may raise costs are not changing a bad power cord on a window A/C unit, not using the air conditioner auto mode, and not using the timer on your unit, in case you’re wondering how to set a timer on an air conditioner. All of these can help reduce electricity usage and save you money.

The answer is a little more complicated for those with a window or portable air conditioning. While it still uses more energy to start an AC unit, powering on these units isn’t nearly as expensive as revving up central AC. Still, if you have things in your house that can be damaged by excessive heat, consider leaving your unit on even if you’re away for a long time.


  • It is rarely a good idea to turn off your central AC unit completely during the summer months.
  • Turning off portable and window AC units is optional, but turning them off entirely when away is sometimes not good.
  • There are many great ways to program your AC to keep down both excess humidity and energy costs while away.

It’s also safer to keep your AC on rather than entirely shutting off because AC units control humidity. This humidity control lessens the likelihood of mold and fungus growing when you’re away. However, this isn’t to say you should always leave it on full blast, and certain thermostat settings will provide the perfect balance of affordability and safety.

For more information on central AC power, we have a great article that shows how to wire a disconnect box for an air conditioner.

Insider Tip

Installing a smart thermostat is a great way to have peace of mind when leaving your AC on when not at home.

Regardless of what type of air conditioning system you have, it’s good to turn off the cooling system when away. Doing this keeps the humidifying aspects operational while keeping energy costs low. On many windows and portable units, an energy-saving button is available to keep energy bills down.

If you know precisely how long you will be gone, you may be able to program your thermostat to stay at a specific temperature and have it turn on to your desired comfort level right before arriving home.

STAT: Experts recommend setting the temperature 7 to 10 degrees higher when not in the house. (source)

Also, for those looking for more info on AC units, we have great articles covering multiple A/C topics including what to do if your lights dim when the air conditioner comes on, how to winterize an air conditioner, how to vent a portable air conditioner, how to fix a portable air conditioner, how to use an air conditioner, and what is a wifi air conditioner.


Check, clean, or replace your air filter before going away for a long trip. A dirty air filter can reduce your AC’s efficiency and lead to greater chances of mildew or mold.


What is the best AC setting for when I’m away?

The setting largely depends on the humidity of the area you live. Still, many HVAC experts recommend setting it at 7 to 10 degrees above your usual temperature.

Do I need to leave the AC for my pet?

In general, it is a good idea to leave it on at some level. It’s also good to know that the bigger the animal, the better they deal with higher temperatures.

Do programmable thermostats work?

Programmable thermostats allow you to set temperature controls and timers and are a proven method for optimizing your AC efficiency.

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