What temperature to set air conditioner in summer?

Set your AC to 78°F when you’re home and awake, 82°F while you sleep, and 85°F when you’re away. This is the schedule ENERGY STAR recommends. The Department of Energy estimates that each degree you raise the setting saves about 3% on cooling costs.

Treat these as a starting point. If 78°F feels too warm, lower it one degree at a time until you’re comfortable. Each degree below 78°F costs more, and some utilities put the cost at 3-5% per degree.

If anyone at home is elderly, very young, or has a medical condition, comfort and safety come before savings. Use a setting that keeps them well.

Why These Numbers

The smaller the gap between inside and outside, the less your AC has to work. Most air conditioners can cool a home only about 20°F below the outdoor temperature. On a 100°F day, an AC running nonstop may hold 78-80°F, and that’s normal. See how long an AC can run continuously.

Setting It Lower Won’t Cool the House Faster

Your AC cools at the same rate no matter what you set. A lower setting doesn’t add cooling power. It only keeps the system running longer, which raises your bill and adds wear. If you’ve been away and the house is hot, set your normal temperature and give it time.

If your AC runs all day and still can’t reach the setting, the setting isn’t the problem. See AC struggling to cool your house and how cold the air from your vents should be. A very low setting can also turn a small airflow or refrigerant problem into a frozen coil: see why your AC keeps freezing up.

What About Sleep?

ENERGY STAR says 82°F for savings. Sleep experts say the opposite: the National Sleep Foundation recommends a bedroom between 60 and 67°F for most adults. Both are right about different goals, and there’s no single correct answer.

• If 82°F is too warm to sleep, lower it one degree at a time until you sleep well. Each degree costs roughly 3%, so choose what you’re willing to pay for.
• Make the bedroom feel cooler without lowering the whole house. Use a fan on you, lighter bedding, and closed blinds during the day.
• Cool the room before bed, then raise the setting if you stay comfortable.

Also Read: Why is my thermostat flashing cool on?

If 78°F Feels Sticky, It’s Probably Humidity

A clammy house at a normal temperature is usually a humidity problem. Lowering the thermostat isn’t the best fix.

• Keep the fan on Auto, so moisture drains away instead of blowing back into the house.
• Use your AC’s Dry mode, if it has one, or a dehumidifier.
• An oversized AC can cause this. It cools fast and shuts off before removing enough moisture.
• Long, steady cycles remove more humidity than short ones.

Also Read: Why is there no power to my thermostat?

When You’re Away

• Gone all day: 85°F, or a setback of about 7°F from your home setting.
• Out for a couple of hours: raise it 3-5°F rather than shutting the AC off. See turning your AC on and off vs. leaving it on.
• If the house feels clammy when you return, use a smaller setback on humid days.

A programmable or smart thermostat helps mostly by automating the schedule, so you don’t have to remember to change it. In winter the same idea applies: see our winter thermostat settings.

Stay Comfortable at a Higher Setting

• Ceiling fans make you feel cooler, but they don’t cool the room. Run them counterclockwise in summer, and turn them off when you leave.
• Close blinds or curtains during the sunniest hours. South- and west-facing windows add the most heat.
• Seal air leaks and add insulation, especially in the attic. A tighter home holds its temperature longer.
• Replace the air filter on schedule. A clogged filter makes the system work harder (how often to replace it).

For more ways to cut your bill, see how to save money on AC in summer.

Common Questions

Is 72°F too cold for the AC?

It won’t hurt the system, but it costs more. Each degree below 78°F adds roughly 3% to your cooling energy.

Is 78°F too hot?

It’s a recommendation, not a rule. Start there and lower it if you’re uncomfortable.

What temperature is best for sleeping?

Sleep experts suggest 60-67°F. ENERGY STAR suggests 82°F for savings. See the sleep section above.

How often should the setting change during the day?

Four changes cover most homes: wake, away, return, and sleep.

Are smart thermostats worth it?

They’re worth it if you’d otherwise forget to change the setting. They don’t save energy if you override the schedule constantly.

When the Setting Isn’t the Problem

If your AC can’t hold 78°F on a normal summer day, has weak airflow, or runs constantly with warm air, have it checked. An annual tune-up before cooling season catches most of these problems early.

If you’re in the Philadelphia area and your AC isn’t keeping up, Cool Aid Co. can find out why.