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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsSet your air conditioner to about 78°F when the home is occupied if that temperature is comfortable for everyone. Raise it during predictable absences and potentially while sleeping, but do not prioritize a fixed energy-saving number over humidity control, comfort, or heat safety.
Start at 78°F—but treat it as a starting point
For most households, 78°F is a sensible summer cooling setpoint when the home is occupied, as long as everyone is comfortable and safe. It is not a medically required temperature, and it will not feel the same in every home. Humidity, sunlight, insulation, air movement, activity level, clothing, and the condition of the air-conditioning system all affect comfort.
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ASHRAE gives a broader recommendation of keeping the thermostat at 76°F or above during the day when the home is occupied and raising it a few degrees at night. In practice, the best rule is to use the highest temperature that keeps the household comfortable without compromising health, then raise the setting when the home is empty.
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Recommended summer thermostat settings
| Situation | Reasonable starting point | How to adjust it |
|---|---|---|
| Occupied during the day | 78°F | Lower it only as much as needed for comfort. A setting of 76°F or 77°F may suit some households, while others may be comfortable at 79°F or higher. |
| Everyone away | Raise the setpoint substantially | The appropriate setting depends on the climate, indoor humidity, pets, plants, building materials, and length of the absence. ENERGY STAR uses approximately 85°F as an example “away” setting, not as a universal requirement. |
| Sleeping | A few degrees higher than the daytime setting | Try 80°F or another slightly higher setting if comfortable. Bedding, ceiling fans, humidity, and personal preference make a difference. |
| Extreme heat | Prioritize safe indoor conditions | Use reliable air conditioning or move to an air-conditioned location. Do not raise the thermostat simply to save energy if the indoor temperature becomes unsafe. |
Why 78°F is not a universal answer
A thermostat measures air temperature at one location. It does not directly measure how comfortable every person feels or whether the whole house is equally cool. A second-floor bedroom with afternoon sun may feel much warmer than a shaded room downstairs even when both are served by the same system.
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Humidity is particularly important. A home can be close to 78°F and still feel clammy if the air conditioner is not removing enough moisture. Oversized room air conditioners can cool the air quickly without running long enough to dehumidify properly. A lower thermostat setting may not solve that problem; the system, airflow, sizing, or drainage may need attention instead.
On humid days, a room air conditioner may remove more moisture when its fan is set to a lower speed, because the air spends more time passing over the cold coil. Follow the manufacturer’s instructions, and avoid settings that create icing or other operating problems.
A practical summer schedule
When the house is occupied
Set the thermostat to 78°F and observe how the home feels over several hours. If people are comfortable, there is no reason to lower it. If the home feels too warm, reduce the setting by one degree at a time rather than making a large change.
Lowering the thermostat far below the desired temperature does not make most central air conditioners cool the house faster. It simply asks the system to run longer. If the system runs continuously but cannot reach the setpoint, that may indicate extreme outdoor conditions, inadequate insulation or airflow, dirty equipment, refrigerant or electrical problems, or an incorrectly sized system.
When everyone is away
Raise the cooling setpoint during predictable absences instead of maintaining the occupied temperature in an empty house. The longer the absence, the more worthwhile a setback may be, although the best value depends on your climate and the time required to restore comfortable conditions.
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- High use of the scheduling feature of the T5 thermostat saved customers between 8 and 16% on heating and cooling bills. Dollar savings range based on nationwide average annual single-family detached home's heat and cooling bills; actual savings varies based on consumption.
- Save Energy and Get Rewarded. Check with your energy provider about available energy savings rebates to save on your purchase. Plus, eligible customers can enroll in their local Utility's "DEMAND RESPONSE PROGRAM" which can reward you for allowing the utility to slightly adjust your AC or furnace temperature settings when there is high energy demand.
- 7-Day Flexible Scheduling or Location Based Temperature Control. It’s your choice. 7-day scheduling programs your thermostat. Geofence technology helps make you comfortable by using your smartphone’s location to know when you’re away and when you return.
- Auto Home and Away Mode. Enjoy ideal temperatures at home, then save when away.
- ENERGY STAR certified. Help save energy, track your heating and cooling with monthly energy reports and get personalized tips on reducing energy use.
Do not use the same away setting automatically in every home. Consider:
- Pets: Their heat tolerance and veterinary guidance may require a cooler home.
- Humidity: A high indoor humidity level can damage materials and encourage mold, even if the air temperature seems acceptable.
- Plants and sensitive materials: Some plants, instruments, finishes, and building contents may not tolerate high temperatures.
- Building response: A well-insulated home may remain comfortable longer than a poorly insulated one, while a home with significant afternoon sun may heat quickly.
- Absence length: A short trip may not justify a large setback if the system must run for a long time to recover.
Approximately 85°F is used as an example daytime “leave” setting in ENERGY STAR programmable-thermostat guidance. Treat that number as an example rather than a target for every household.
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At night
Try raising the thermostat a few degrees above the daytime occupied setting. Many people sleep comfortably at a slightly warmer temperature, especially with appropriate bedding and a ceiling fan. If the bedroom remains humid or uncomfortable, return to the lower setting or investigate the cause rather than sacrificing sleep.
Heat safety comes before energy savings
Do not follow a fixed energy-saving temperature if it leaves anyone in the home at risk. During dangerous heat, public-health guidance is to use air conditioning or find an air-conditioned location. Older adults, young children, pregnant people, people with chronic medical conditions, and people taking medications that affect heat tolerance may need additional protection and a cooler environment.
Fans can improve comfort, but they are not a replacement for air conditioning during extreme heat. The CDC warns that fans may increase body temperature when indoor temperatures exceed 90°F. If the home is becoming dangerously hot, use air conditioning, seek a cooling center or another air-conditioned location, and follow local heat advisories.
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Use fans to feel cooler—not to cool an empty room
A ceiling fan moves air across the skin and can make occupants feel cooler, allowing the thermostat to be set a little higher. It does not lower the actual temperature of the room. Turn a ceiling fan off when nobody is using the room; otherwise it consumes electricity without providing personal cooling.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchFans are best viewed as a comfort aid alongside air conditioning. They should not be relied on alone during hazardous heat, particularly for people who are more vulnerable to heat illness.
Should you use a programmable or smart thermostat?
A programmable thermostat can automate occupied, away, and sleep settings so the household does not have to remember to adjust the temperature manually. An ENERGY STAR certified smart thermostat may add app-based control and may use occupancy, temperature, or learning data to modify the schedule.
ENERGY STAR reports average savings of approximately $50 per year for certified smart thermostats, with savings potentially reaching about $100 per year in homes with high heating and cooling bills. These are reported averages and possibilities, not guarantees. Actual results depend on climate, occupancy, equipment, existing thermostat habits, schedule accuracy, and how much the household changes its settings.
If automatic scheduling or remote control would help your household, compare an ENERGY STAR certified smart thermostat. Before buying, confirm that the model works with your specific system and wiring. Important compatibility questions include:
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- Does the system use single-stage, two-stage, or multi-stage heating or cooling?
- Does it have auxiliary or emergency heat?
- Is a common wire, often called a C-wire, required or included in the installation plan?
- Does the thermostat support the existing number of wires and terminals?
- Does the HVAC manufacturer recommend a particular control for a variable-capacity system?
Variable-capacity equipment may perform best with the manufacturer-recommended thermostat. If the wiring or system configuration is unclear, have an HVAC professional verify compatibility before purchasing or installing a control.
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- PRIVACY PROTECTION: Sensi won’t sell your personal information to third parties or leverage your thermostat activity data for targeting or advertising purposes
- CONTROL FROM ANYWHERE: The top-rated mobile app for Android and iOS devices makes it easy to control your comfort from a smartphone or tablet
Some utilities offer smart-thermostat rebates or discounts, but eligibility, qualifying models, rebate amounts, and deadlines vary by ZIP code and utility territory. Check the current program for your address before assuming a rebate applies.
Keep the air conditioner capable of reaching the setpoint
The thermostat can request cooling, but it cannot compensate for restricted airflow, dirty coils, duct losses, inadequate insulation, or failing components. A small maintenance routine helps the system operate as intended.
Monthly cooling-season checklist
- Check the air filter about once a month. Clean a reusable filter or replace a disposable one when it is dirty. Verify the filter size and the system’s requirements before purchasing a replacement.
- Keep supply and return vents open and unobstructed. Furniture, rugs, curtains, and stored items can restrict airflow.
- Inspect the outdoor unit. Remove leaves, grass, and other debris from around the equipment while following the manufacturer’s clearance requirements.
- Watch for unusual symptoms. Weak airflow, ice on refrigerant lines, water near the indoor unit, unusual odors, short cycling, or a system that cannot reach its setpoint should be investigated.
Annual pre-season service
Schedule a professional cooling-system check before the hottest part of the season. A thorough inspection may include the evaporator and condenser coils, refrigerant level, blower components, electrical connections, controls, condensate drainage, and overall airflow. Sealing duct leaks, improving insulation, and reducing solar heat gain can also improve comfort and reduce the load on the system.
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Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What to do if 78°F still feels uncomfortable
- Check humidity. If the house feels clammy, the issue may be moisture removal rather than temperature alone.
- Check the filter and airflow. A dirty filter or blocked return can reduce performance.
- Close blinds or shades on sunny windows. Reducing solar heat gain can improve comfort in the affected rooms.
- Use a ceiling fan only where people are present. This can improve perceived comfort without lowering the thermostat for the entire home.
- Compare rooms. A single hot room may point to ductwork, insulation, air sealing, or zoning problems.
- Have persistent problems assessed. If the system runs continuously, leaks water, freezes, cycles unusually, or fails to maintain the setpoint, arrange a professional air-conditioner inspection rather than repeatedly lowering the thermostat.
The simplest decision rule
Start at 78°F while occupied. Raise the setting when the home is empty or while sleeping if that remains comfortable. Lower it only as much as necessary for comfort, and address humidity, airflow, sunlight, insulation, or equipment problems when a lower number does not solve the underlying issue. During extreme heat, protect people first: use dependable air conditioning or move to a cooler, air-conditioned location.
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.Connectivity : Wi-Fi - 802.11b/g/n 2.4 GHz, 802.11a/n 5 GHz Wi-Fi., Wireless interconnect : Bluetooth Low Energy Please refer to the product description section below for all applicable legal disclaimers.Product note: You can also check your system’s compatibility before purchasing a Nest thermostat with our online Nest Compatibility Checker on the Google Nest support page
- The Nest Thermostat is designed to work without a C wire in most homes, but for some systems, including heating only, cooling only, zone controlled, and heat pump systems, you’ll need a C wire or other compatible power accessory
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home. Lock feature: No
- Programmable thermostat that lets you create an energy efficient schedule in the Google Home app on your Android or iPhone
- Remote control lets family members change the thermostat temperature from anywhere on a phone, laptop, or tablet[1]
Frequently Asked Questions
Is 78°F really the best air-conditioner setting in summer?
78°F is a reasonable energy-saving starting point for many households when the home is occupied, but it is not a universal requirement. Adjust it for comfort, humidity, activity, sunlight, insulation, and the needs of vulnerable occupants.
What temperature should I set the AC at night?
Try raising the thermostat a few degrees above the daytime setting, provided the bedroom remains comfortable and humidity is controlled. A ceiling fan can improve perceived comfort, but it does not cool the room itself.
What temperature should I leave my AC at when I am away?
Raise the setpoint during predictable absences rather than cooling an empty home to the occupied temperature. ENERGY STAR uses approximately 85°F as an example away setting, but the appropriate value depends on climate, humidity, pets, plants, building materials, and the length of the absence.
Why does my AC run constantly but not cool the house?
Not necessarily. If an air conditioner runs continuously but cannot reach the setpoint, check the filter and airflow and look for issues such as blocked vents, dirty coils, duct losses, or inadequate insulation. Persistent problems require professional assessment.
The Bottom Line
For most homes, set the air conditioner to about 78°F when occupied, raise it during predictable absences and possibly at night, and adjust for humidity, comfort, and health. The best setting is the highest temperature that keeps the household comfortable and safe.
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