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What is the Best Temperature to Set an Air Conditioner’s Thermostat?

 

Some of us enjoy a very cool indoor climate in summer; others just want to make it bearable.  Is there an optimal temperature to set the thermostat?  Personal preference aside, what is the best temperature to set the thermostat during air conditioning season?  This home HVAC guide takes a look at that, including the benefits involved.

Set your Thermostat for 78 Degrees for Air Conditioning

The truth is, if you want the most energy efficient setting, choose the highest temperature at which you are comfortable.  If that’s 78, that’s great.  If it’s 80, that’s even better.  Most home energy experts choose 78 degrees F as the “magic” temperature that should keep most homes comfortable without producing exceptionally high utility bills. An air conditioner running enough to maintain 78 degrees will also run long enough to remove plenty of humidity from your home.

Keep in mind that 78 degrees in air conditioning can be much more comfortable than 78 degrees outside.  First, you won’t be sitting in the sun while indoors, something that can make you very uncomfortable.  Secondly, air conditioners are like whole-house dehumidifiers.  They remove a large amount of humidity from the house.  We feel cooler at higher temperatures when there is less humidity. You may feel as comfortable with an air temperature of 78 or 80, with 40% humidity as you would at 72 or 74 degrees with 80% humidity.

Energy Savings with 78 Degrees

While the exact number varies based on the energy-efficiency of your air conditioner and the insulation qualities in your home, you can save between 15% to 25% on your energy use by setting the thermostat at 78 rather than 70 or 72. Factor 2-3% per degree.  That adds up significantly during the course of a long cooling season.

Other Ways to Reduce Energy Use while Air Conditioning

There are a few other things you can do to reduce energy use during the air conditioning season and still keep your home comfortable.  First, raise the temperature to 85 degrees when you’re gone.  Use a programmable thermostat to raise the temperature when you leave and lower it again shortly before you plan to get home. Secondly, use a low-constant fan setting on your furnace or air handler if it is equipped with one.  Trane’s Comfort-R system is one example.  The fan runs on low even when the AC isn’t running. This reduces humidity even more than the typical functioning of the air conditioner.

Thirdly, if you get a new central air conditioner, make sure it is sized correctly.  Most air conditioners are ½ ton to 1 ton too large.  When the AC is too large, it cools the house too quickly, not removing enough humidity in the process.  The result is a clammy feel in your home. You’ll have to turn down the thermostat even further to get the humidity control you want. Finally, set the thermostat and leave it alone.  Turning the thermostat down to 70 won’t cool off your house when it’s 85 any quicker than setting it to 78.  If you set it low, you run the risk of forgetting to adjust it upwards and wasting a lot of energy.  Use a programmable thermostat and then leave it alone as much as possible.

Summary

From a comfort standpoint, everyone is a bit different.  From an energy standpoint, setting the thermostat to 78 should help you stay comfortable while also keeping your warm weather utility bills under control.

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