Since air conditioners use more energy when they cycle all day, it is cheaper to let your system operate at full capacity when you're home instead of running it at a lower capacity all day. The more energy you use, the more money you'll pay in monthly utility bills.

In general, an air conditioner runs for about 20 to 25 minutes until it reaches the desired temperature, then turns off and recycles throughout the day and night. An air conditioner should run for 10 to 15 hours a day on typical summer days.

The short answer is an hour or so in moderately hot weather, but the time frame is quite variable depending on the humidity of the day, air leakage into the house, sun exposure on the glass etc.

Estimated Energy Savings from Turning AC Off at Night It probably won't surprise you to learn that a central AC system uses far more energy during the day than at night. In hotter, more humid climates, somewhere around two-thirds of the system's total energy consumption occurs between the hours of noon and midnight.