What Temperature Should You Set Your AC to When Away in Summer?

What Temperature Should You Set Your AC to When You’re Away During Summer?

For a typical workday, try setting the air conditioner about 5°F to 7°F higher than your usual occupied setting, then adjust based on how the house feels when you return. If you normally keep it at 75°F, that means starting around 80°F to 82°F. For a quick errand, changing the thermostat may save little. For a full day away, a larger setback may be reasonable, but the right limit depends on humidity, pets, and how quickly your home cools down.

There is no single safe “away” temperature for every house. A setting of 85°F may be workable in some dry climates and unsuitable in a humid home where moisture builds up while the AC is off. The useful question is how high you can let the indoor temperature rise without creating a problem for the people, animals, or belongings inside.

Match the setting to the time you’ll be gone

Air conditioners remove heat from a house. As the indoor temperature rises closer to the outdoor temperature, heat enters more slowly, so the AC has less work to do during an absence. That is why raising the thermostat can reduce electricity use. The savings depend on how long the higher setting lasts and how much cooling the house would otherwise need.

For an errand lasting an hour or two, leaving the thermostat alone is often simplest. A well-insulated house may barely warm up in that time. If you have a programmable thermostat, you could raise the setting a few degrees, but there is little reason to make a large change just before a short trip.

A workday gives the house more time at the higher setting. Start with a 5°F to 7°F increase and see what happens over several days. A household comfortable at 74°F might try 79°F to 81°F while everyone is out. If the house stays reasonably dry and cools down before anyone gets home, you may be able to raise the away setting further. If it takes hours to recover, use a smaller increase or start cooling earlier.

For an entire day away, including an evening out, you may have more room to raise the setting because no one needs the house cooled by late afternoon. Avoid treating a particular number as a target to reach. An empty house in a dry climate may tolerate a higher setting than one in a humid area, and an “empty” house with a dog or cat is not empty for thermostat purposes.

Give the house time to cool before you return

Setting the thermostat much lower than your preferred temperature does not make a typical air conditioner cool faster. If you want the house at 75°F when you get home, set it to 75°F and allow enough time for the system to reach it.

Recovery time varies. Insulation, attic heat, window exposure, outdoor temperature, and the size and condition of the AC system all affect how quickly indoor temperatures fall. A shaded, well-insulated house might recover from a modest setback fairly quickly. A house with west-facing windows may still be gaining heat late in the afternoon, just as the AC is trying to cool it.

A programmable or smart thermostat can handle this without requiring you to remember a daily adjustment. Set an away temperature for the hours you are usually out and schedule your preferred temperature to begin before you return. Some thermostats offer a recovery feature that learns when to start cooling to reach the target by a chosen time. Check how yours works rather than assuming it will cool the house by your arrival.

Use a few ordinary summer days to test the schedule. Note the indoor temperature when cooling begins and whether the house reaches your preferred setting on time. If it does not, start cooling earlier or reduce the daytime setback. During a heat wave, the same schedule may need more recovery time.

Watch indoor humidity, not just temperature

In humid weather, the thermostat reading tells only part of the story. A central air conditioner removes moisture while it runs. Raising the cooling setting can mean fewer cooling cycles, allowing indoor humidity to climb even when the temperature looks acceptable.

A separate indoor hygrometer can help you see what happens while you are away. The U.S. Environmental Protection Agency recommends keeping indoor relative humidity below 60%, ideally between 30% and 50%, to help limit mold growth. If humidity repeatedly rises above 60% during your absence, reconsider the away setting and look for moisture sources or ventilation problems. A musty smell or condensation also deserves attention.

Lowering the temperature is not the only possible response. A properly sized dehumidifier may help in a persistently damp home, though it uses electricity and must be set up and maintained correctly. If you have a thermostat with a humidity-control feature, check what equipment it controls and how it operates. Simply setting the AC fan to “on” is not a substitute for dehumidification; continuous fan operation can sometimes return moisture from a wet cooling coil to the air.

Humidity is a reason to be cautious with advice to set every empty house to 85°F. In some homes, the AC may run too little at that setting to control moisture. Indoor readings, not a universal number, should guide the decision.

Account for pets and heat-sensitive belongings

Pets need a temperature they can tolerate for the whole time you are away, including the hottest part of the day. Their needs vary with species, age, health, coat, and access to water and cooler rooms. Animals with breathing problems, older pets, and some short-nosed dog breeds can be especially vulnerable to heat. Ask your veterinarian about an appropriate indoor range if your pet has a medical condition or you are unsure what is safe.

Do not choose an away setting for a pet based only on the temperature displayed when you leave. A sunny room can become much warmer than the hallway where the thermostat is mounted. Close blinds where direct sun heats the room, provide fresh water, and make sure the pet can reach a cooler area. If the AC fails during an extreme heat event, a thermostat setting offers no protection; consider how someone could check on an animal if you will be gone all day.

Most ordinary household items do not require the same temperature you prefer for comfort. Some belongings do need more care. Medications should be stored according to their labels, and certain electronics, musical instruments, artwork, and photographs may be sensitive to heat or humidity. Check the requirements for anything valuable or difficult to replace before allowing the house to get substantially warmer.

Find a setting that works in your house

A practical away setting is one that reduces cooling while keeping indoor conditions within acceptable limits. Start with a moderate increase for a workday, then check three things: the highest indoor temperature reached, the humidity level, and how long the AC takes to bring the house back to your preferred temperature.

If all three are acceptable, try another small increase. If the house feels damp, a pet’s room gets too hot, or cooling runs long after you return, lower the away setting or change the schedule. Outdoor conditions will change the result, so a setting that works in June may need adjustment during a hotter, more humid stretch in August.

For short absences, a change may not be worth the trouble. For a regular workday, a 5°F to 7°F increase is a sensible place to begin. For longer absences, let your home’s temperature, humidity, and recovery time determine how far you go.