When You Leave Home, Should You Turn Off Your Air Conditioner?

A recent study has the answer, and it's more complicated that a simple "yes" or "no." It depends on several factors, including what kind of air conditioner you have.

Summer may be coming to an end, but many parts of the country will still need air conditioning well into the fall. Mindful of utility bills, some of you may be wondering, “What’s the most efficient way to use my air conditioning?”

Two professors and one Ph.D student at the University of Colorado, all engineers, tried to determine whether shutting off your air conditioning during the day when you’re not home actually saves money. According to their study, it depends on how much energy it takes to remove heat from your home.

Multiple factors come into play, like how well your home is insulated, your climate and what kind of AC unit you have. The better insulated your home, the less heat will enter during the day. This will reduce the load on your AC. Likewise, humidity and your system type also have an impact.

The researchers looked at two climates, three systems and three cooling cycles. They also standardized the time of day, making sure to include the hottest part. Accounting for various experiences helped them address the question: Should you leave your air conditioner on when you leave home?

Curiously, the most efficient air conditioning systems did not always yield the highest energy savings. And different factors can affect your specific situation. But generally, the answer is yes.

Overall, by leaving the AC off for eight hours, you’ll see energy savings no matter what type of system you have. Leaving it off for four hours yielded mixed results. Depending on the humidity and the system, it could result in minor energy savings, or take a little more energy than running it all day.

One thing the study didn’t account for was the cleanliness of the system. A dirty air conditioner won’t cool as efficiently. Don’t forget to clean your unit regularly to keep it functioning well.

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