It's Settled: This Is the Best A/C Temperature for Your Home

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Your air conditioning may feel like a miracle in the summer months, but in reality, it's simply a machine. This means that it has its limitations and can only do so much. Proper and thoughtful use of your cooling machine — namely, finding the right thermostat settings — saves wear and tear on the system and saves you money on your energy bill.

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Is your family always fighting over the best temperature for the A/C? Here are the definitive answers to the best A/C temperatures for everyday use, energy-saving, and sleeping.

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The best air conditioner temperature for balancing comfort level and energy efficiency is 78 degrees Fahrenheit, according to the United States Department of Energy.

What Should I Set My A/C To?

The United States Department of Energy recommends setting your thermostat to 78 degrees Fahrenheit for the best mix of comfort and energy saving. This suggestion is met with quite a bit of hostility, however, as many people believe this setting is far too warm. It's also not a hard and fast rule, as you may feel more comfortable at a different temperature setting, which is, after all, the point of having air conditioning.

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To find the most comfortable A/C temperature, start at the suggested 78 degrees and go from there. If you're still too hot, drop the temperature 1 degree at a time until you find the setting you prefer. In other words: Don't just pick an arbitrary number that you think will work. Doing so may mean that you set your air conditioner to 70 degrees, for example, when you would be perfectly comfortable at a warmer (and cheaper) 75 degrees.

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What's the Best A/C Temperature for Sleeping?

The optimal A/C temperature for sleeping is a slightly chilly 60 to 67 degrees Fahrenheit. However, having a bedroom temperature that low can prove costly. Luckily, there's a good solution: Simply turn your air conditioner down a few degrees from the recommended 78 right before you go to bed. Turn down the air only as far as you need for the ideal sleeping temperature.

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A good rule of thumb is that if you find you need a thick blanket to be comfortable and sleep well, your A/C is set too low. Sleeping with a ceiling fan on can also help you keep your room cool without relying on your air conditioner to do all the work.

What's the Best A/C Temperature for Energy Saving?

The Department of Energy suggests that 78 degrees Fahrenheit is the best A/C temperature for creating a balance between comfort and energy consumption during the day. It also recommends setting the thermostat to about 85 degrees when you're away or at work. This will save you money without overtaxing the air conditioner when you're home and it's time to cool things down again.

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You can also save with a programmable thermostat. These can automatically change the temperature to keep your home warmer during the day but automatically have things cooled back down by the time you get home from work. These allow you to set just the right thermostat temperature and adjust it as needed even when you're not home. A smart thermostat does the same, but it learns your cooling habits and adjusts itself automatically.

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In general, however, the closer you set the indoor temperature to the outdoor temperature, the less energy your air conditioner will use. You can also save up to 10 percent per year on cooling costs by simply turning your air conditioner down 7 to 10 degrees for eight hours a day.

Tips for Saving on Cooling Costs

Fortunately, there are a lot of things you can do to help save money on your A/C bill. Try one or all of the following tips:

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  • Close the curtains and blinds during the hottest part of the day.​ This will prevent the sun from heating the space.
  • Make sure your thermostat isn't in direct sunlight.​ A thermostat baking in sunlight will read high and think you need your air conditioner when you don't.
  • Install ceiling fans in rooms you use frequently.​ The direct airflow from ceiling fans helps your skin release body heat, making you cooler. Fans do not cool the air, so there's no point leaving them on in an empty room. A ceiling fan allows you to adjust your air conditioner temperature up by 4 degrees without noticing a difference in comfort. Although energy costs can vary widely, it costs an average of 58 cents per hour to run a central air conditioning unit and 1 cent per hour to run a ceiling fan.
  • Let the temperature cool down gradually.​ Another way to save is to stop turning the air conditioning way down for faster relief. It's common for people to come home and bump their thermostat down lower than usual for a few minutes to cool things off quickly. Unfortunately, this does nothing but waste money. Your air conditioner cools the air at a certain rate, and you can't make it work any faster. Turning down the thermostat will just make the unit run longer as it strives to reach the new temperature setting.
  • Don't heat up your house with other appliances.​ You may not be able to make your A/C unit run any faster, but you can help it by making sure you're not competing with it. Refrain from using the oven, clothes dryer, and other heat-generating appliances during the warmest part of the day. These heat your home while the air conditioner attempts to cool it, resulting in a costly energy use tug of war.
  • Pay attention to the weather.​ If the temperature outside dips low enough at night, you may not even need your air conditioner. Open the windows and let in some cool air. In the morning, close everything back up to keep the air cool as long as you can and then turn the air conditioner back on. Turning the unit on and off frequently does no harm.
  • Maintain your A/C.​ Regular filter changes and an annual cleaning and servicing of your HVAC system can also help you lower your electricity bills by keeping your air conditioner running as well as possible. Dirty coils and evaporators can make your air conditioner work harder, as can low refrigerant levels. When it's time to replace your A/C, make sure you buy one that bears the Energy Star logo.

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Is My Thermostat Reading Accurately?

If your thermostat reading says you should be comfortable but you're not, there could be a problem with the thermostat itself. To test the thermostat, grab a thermometer and compare the readings. You can't, however, just place a thermometer in the room and see what happens. To check your thermostat accurately, you need the thermometer to be near it. Here's how to test a thermostat with a thermometer:

  1. Hang a paper towel on your wall next to the thermostat with a piece of tape.
  2. Tape the thermometer to the paper towel and then wait at least 15 minutes. (The paper towel ensures you are measuring the room temperature and not the wall temperature.)
  3. When the time is up, compare the readings on the thermometer and thermostat with each other. If the temperatures don't closely match, your thermostat may need some attention.

Make sure the thermostat is level on the wall. If it is, remove the cover and blow or brush out any dirt and debris that may be interfering with the contacts inside the unit. If these tricks fail, it's probably time for a new thermostat.

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