Should You Turn Your AC Up When You're Not Home?

Don't turn off the unit entirely if you're simply going to work. "If you're just leaving home for the day, it's more energy efficient to keep your air conditioning turned on – but turn it a few degrees higher than you might set it for comfort if you were at home," Kureczka says via email.

The same directions apply if the house is going to be unoccupied for only a day or two. "It's more energy efficient to keep the unit on but turn the temperature setting up," she advises.

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Turning off the AC unit during the day is not necessarily a bad thing — it is a myth that the AC unit has to work extra-hard to cool off a hot house. It runs at the same speed either way — it just will have to stay on longer to cool off a hot dwelling. In fact, the unit may use more energy if it is left on all day at the normal temperature than if you turned it off and turned it on in the evening.

That said, if you live in a hot climate, it could take several hours to cool off your house by which time you may be ready for bed. Also, central air conditioning is not just about cooling your space. It also drastically reduces humidity levels. When the system is shut off for more than a few hours, the humidity level will start to rise, which can result in mold growth, damage to electronic items and the warping of wood and paper. Any pets left in the house could also be at risk of overheating and discomfort. This is especially likely in hot, humid climates, like Florida's.

This is why it's recommended to keep the AC on but raised to a higher temperature. The DOE points out that a higher interior temperature actually slows the flow of heat into your house, thus saving energy and money.

When you get back home, don't turn the AC super-low to "speed up" the cooling process. Your home won't cool any faster and you'll just add to your energy bill.

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