When Is the Best Time to Turn On the AC?

Many HVAC experts say that when the outdoor temperature hits 75 degrees Fahrenheit,  it’s time to turn on the air conditioner. While the mid-70s would normally indicate late spring or early summer weather, the climate in your region might have a mind of its own. That’s why it’s important to consider a variety of factors, including personal preference, when deciding when to turn on your AC.

When to Turn On Your AC

When your home reaches 75 degrees inside, it’s a good idea to turn your AC on. If cool air isn’t blowing as it should, then you’ve given yourself plenty of time to hire a local AC installer or HVAC pro to fix it before you really need it. 

Aside from that initial test run, here are three factors to consider when determining an appropriate time to turn on the AC:

Interior Temperature

While it’s best to go by the outdoor temperature—again, 75 degrees is a good starting point—rather than the calendar, it also depends on how you’re feeling indoors. Sometimes, temperatures swing wildly, so if it’s in the 70s during the day but dropping down to the 50s at night, your home’s internal temperature may be just fine without the AC on.

Personal Preference

Even if the outdoor temperature has been steadily in the mid-70s, you might find that turning on a ceiling fan or opening a few windows for some cross-ventilation is enough to keep things comfortable. Remember: It’s your house, your rules, and, ultimately, your utility bill.

Windows and Insulation

If you’ve got energy-efficient windows and good insulation, your home might stay cooler for longer, even as outdoor temperatures rise. This is also important for keeping your home warm in the winter. If you’ve got poor insulation or drafty windows, it’s worth it to repair or replace them to conserve energy and lower your monthly utility costs.

When Is the Best Time to Turn On the AC During Summer?

Even during the dog days of summer, the outside temperature will drop overnight for one very simple reason: The hot sun has set. 

Whether you have central air, a mini-split unit with a programmable thermostat, or you simply press a button on a window AC unit, do so in the mornings during the summer. The internal temperature will be lowest then, so turning on the AC early in the day will ensure that it has time to cool off the space.

Wait any longer and the temperature will continue to rise, making your AC work even harder than it usually does. This is bad news for the longevity of your appliance and the size of your utility bills.