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For most homes, reduce cooling when nobody is there instead of holding the occupied temperature all day. Raise the thermostat setpoint or use an away schedule. Turning the system fully off can also make sense in some conditions, but humidity, pets, plants, health needs, equipment limits and the length of the absence matter.
The practical answer: use a setback, not an automatic all-day hold
Cooling an empty house to the same temperature used while people are home generally wastes energy. A higher cooling setpoint during work, school or sleep hours reduces the time the air conditioner needs to run. A programmable or smart thermostat can restore the normal setting before you return.
The U.S. Department of Energy (DOE) says homeowners should consider leaving central air conditioners off during unoccupied hours or using a programmable thermostat. That guidance supports reducing operation while away, but it does not establish one universal away temperature or a universal rule that every system should be shut down completely.
Do not rely on the claim that restarting always cancels the savings because the unit must work harder. The official guidance is mixed: DOE purchasing guidance supports off-hours shutdown or scheduling, while an older 2021 DOE consumer guide warns that summer shutdown can permit moisture buildup. The dependable conclusion is to reduce cooling while away and account for humidity and household needs.
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- An Alexa thermostat - Amazon Smart Thermostat is an easy way to switch from a traditional thermostats for homes and help reduce energy usage.
- Create comfort zones throughout your home by connecting to select Alexa devices to automatically adjust heating and cooling based on temperature readings or presence detection.
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- Save energy - According to EPA estimates, ENERGY STAR certified thermostats save an average of $90 on yearly energy bills.
- Programmable thermostat and automatic control - Create your own home, away and sleep schedules, or have Alexa automatically control the temperature with Alexa+ advanced features.
Central air: the best default settings and schedule
Raise the setpoint when the house is empty
Set the thermostat warmer for unoccupied periods rather than maintaining the usual occupied temperature. The reviewed DOE material does not prescribe a single correct away setting, so choose a level that protects occupants, pets, plants and the building in your climate.
Automate the change
A programmable thermostat can apply weekday, weekend and sleep setbacks. A compatible smart thermostat may add remote control, learning features or absence detection. These features are optional: manual adjustments cost nothing, and compatibility with your heating and cooling equipment should be confirmed before buying.
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- Save up to 23% every year on heating and cooling costs, adjusts to your set schedule to save energy when you’re gone and optimize comfort when you’re home. Compared to a hold of 72
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- Change your temperature by easily tapping the color touchscreen or using the ecobee app. Plus, free software upgrades ensure you get the best out of your Smart Thermostat Essential, for years to come
- Automatically adjusts to your set schedule to save energy when you’re gone and optimize comfort when you’re home. Keep track of your energy consumption when you're on the go on the ecobee app
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Restore comfort before arrival
If your thermostat supports scheduling, have it return to the occupied setting before people arrive. That avoids keeping the home at the lower setting during the entire absence while still allowing a comfortable return.
When full shutdown deserves caution
DOE’s 2021 consumer guide cautions that turning a summer system off can allow moisture to build up and potentially contribute to mold. That is a consideration, not a prediction that every home or every absence will develop a problem. Warm, humid weather, poor moisture control and vulnerable building materials increase the importance of maintaining a suitable setpoint.
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- ENERGY STAR certified smart thermostat for home that helps you save energy and stay comfortable.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.Connectivity Protocol : Wi-Fi.Connectivity Protocol : Wi-Fi
- 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. Lock feature: No
- Nest Thermostat turns itself down when you leave, so you don’t waste energy heating or cooling an empty home; easily program 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]
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- Use a suitable setting rather than full shutdown if indoor humidity is a recurring problem.
- Account for pets, plants, medical needs or anyone who remains in the home.
- Follow the equipment manual where it specifies minimum or maximum operating conditions.
- For an extended absence, arrange a check of the property if a plumbing, humidity or storm risk makes unattended conditions concerning.
The sources reviewed do not establish a universal number of hours or days after which shutdown becomes the right choice. Base the decision on the home and its conditions, not a fixed duration slogan.
Window and room air conditioners work differently
A room unit has its own thermostat and normally cycles its compressor as the room reaches the target temperature. It is not controlled like a whole-home central system, so a central thermostat recommendation does not automatically apply.
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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]
Use the unit’s controls
Set the room-unit thermostat as high as is comfortable. ENERGY STAR commonly suggests 78°F as a general room-air-conditioner setting, not as a universal comfort or health requirement. Turn the unit off or raise its setting when the room is unoccupied if humidity and household needs allow.
Size and installation affect the result
An oversized room unit does not cool better and can waste energy. Correct sizing, a well-sealed window opening and unobstructed airflow help the unit operate as intended. Connected room air conditioners may provide remote and scheduled control.
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- SAVE ABOUT 23% ON HVAC ENERGY*: The ENERGY STAR-certified Sensi smart thermostat can help you save energy with features like flexible scheduling, remote access and usage reports
- SIMPLE CONFIGURATION: Looks and feels like a thermostat. Has buttons and fits the same space as a traditional thermostat so you don’t have to patch and paint your walls
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| Situation | Useful control | Main qualification |
|---|---|---|
| Central air | Thermostat setback, programmable schedule or compatible smart thermostat | Consider whole-home humidity, occupants, pets and equipment guidance before full shutdown. |
| Window or room unit | Unit thermostat, timer or connected schedule | Correct sizing and window sealing matter; a whole-home thermostat is not a fit for every room unit. |
| Manual control | Raise the setpoint or switch the unit off before leaving | Costs nothing, but depends on remembering each time. |
| Automated control | Programmable or smart thermostat/connected unit | Check compatibility; purchase is optional. |
How much can you save?
A 2021 DOE consumer guide says thermostat setbacks while away and while sleeping can save as much as 10% on heating and cooling costs. That is a qualified potential estimate for combined heating and cooling, not a guaranteed air-conditioning-only result. Your outcome depends on climate, electricity rates, insulation, equipment efficiency, setpoints and how long the home is unoccupied.
No reviewed source provides a bill figure for a particular home or a universal savings percentage for switching an air conditioner fully off and back on.
Maintenance still matters
Energy savings from scheduling can be undermined by restricted airflow or neglected equipment. ENERGY STAR recommends inspecting, cleaning or changing central HVAC filters monthly and arranging seasonal checkups. Use the filter size and replacement interval specified for your system, especially where dust, pets or renovation work increase loading.
A simple decision checklist
- Identify the equipment: central air, window unit or another room system.
- Decide whether anyone, any pet or any plant remains in the home.
- Check whether humidity has caused condensation, odors or mold concerns before using a full shutdown.
- Raise the cooling setpoint or program an away period.
- Schedule a return to the occupied setting when practical.
- Verify thermostat or connected-unit compatibility before purchasing new controls.
- Keep filters maintained and follow the equipment manual.
Should you buy a smart thermostat?
An ENERGY STAR-certified smart thermostat can automate away and sleep setbacks, provide remote adjustment and, on compatible systems, detect absence. It is a convenience and control option—not a requirement for saving. Confirm wiring and equipment compatibility before purchase; manual setbacks deliver the core benefit without a new device.
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Utilities may offer incentives for ENERGY STAR-qualified equipment, but eligibility and availability vary by location and should be checked with the current local program.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
