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How Many Watts Does a Window AC Use? Tips, Facts, & FAQ

Window air conditioner

Temperatures can get quite high across most of the United States during the summer months, and many people look for ways to keep cool. Air conditioning is one of the best tools for reducing temperatures, but it uses much more power than a common fan and raises electric bills. The more watts the unit uses, the more it will cost each month. Unfortunately, air conditioners come in different sizes. They can use different wattages, so it’s hard to say exactly how much your unit uses, but the average is a little under 900 watts. Keep reading as we discuss why some units use more watts than others.

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How Many Watts Does an Average Air Conditioner Use?

Air conditioners in the United States typically use between 400 watts and 2,500 watts to cool a home. The average is 884.2 watts, but the most popular air conditioners use about 660 watts.

window air conditioners used in a residential building
Image Credit: Chromatograph, Unsplash

How Do I Know How Many Watts My Air Conditioner Uses?

You can often find out how many watts your air conditioner uses by looking at the packaging or reading the owner’s manual. You can also multiply the number of amps by the number of volts or divide the British Thermal Units (BTU) by the Energy Efficiency Rating (EER).

Formula Example
Amps x Volts = Watts 4 amps x 110 volts = 440 watts
BTU/EER = Watts 5,000 BTU/ 12 EER = 416.6 watts

Average Wattage per BTU Rating

You can also use this chart to avoid the math and get a ballpark estimate of how many watts your air conditioner uses if you know the BTUs, which companies almost always print on the packaging.

5,000 400–625
6,000 500–750
8,000 650–1,000
10,000 800–1,250
12,000 1,000–1,500
15,000 1,250–1,900
18,000 1,500–2,250
window air conditioners on a building in new york
Image Credit: Tim Hüfner, Unsplash

How Do I Choose the Right Air Conditioner for My Home?

You will need to choose an air conditioner based on the size of the room. The larger the room, the larger the machine will need to be to keep it cool. Small rooms of about 150 square feet will only require a small 5,000 BTU unit, while a large 1,000-square-foot room will likely require a considerably larger 18,000 BTU unit. To get the square footage of your home, multiply the length and width.

Formula Example
Length x Width = Square Feet 12 x 12 = 144 square feet

BTU per Square Foot

Once you take the measurements of the space that you are trying to cool, use this chart to help you choose an air conditioner based on its BTU rating.

Room Size in Square Feet BTU
150 5,000
300 7,000
450 10,000
550 12,000
650 14,000
1,000 16,000–18,000

Low-Wattage Air Conditioners

Low-wattage air conditioners use fewer than 600 watts to cool a home, and though they use far less power than average, they make up almost 20% of the market. These units are perfect for people who only need to cool a small area and want to minimize their carbon footprint while reducing costs. Low-wattage air conditioners are also good for use with a generator, as high-powered units can have too much of a startup spike.

Wall mount air conditioner
Image Credit: Kskhh, Wikimedia Commons CC SA 4.0 International

Other Tips and Things to Remember

  • If your air conditioner has a rating of 400 watts, it will only use that much power when running at full. However, many models have multiple settings that use much less energy during operation.
  • Look for a unit with a high Energy Efficiency Rating (EER, CEER, SEER) to save power and cool your home faster. Always compare units with the same kind of rating.
  • Make sure there are no lamps or other devices that might throw off heat near your air conditioner’s thermostat, causing it to stay on longer than required.
  • Keep the filter clean to minimize strain on the unit and to prevent it from running longer than it should.
  • If the room that you are trying to cool is extra sunny, add 10% to your BTU calculations.
  • If the room that you are trying to cool has a door to the outside, add 10% to your BTU calculations.
  • If you expect more than two people in the room continuously, add 600 BTU to your calculations for every additional person.
  • Add 4,000 BTU to your calculations if you plan to put the air conditioner in a kitchen.

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The average American window air conditioner uses about 884 watts. However, many people use a small unit, and the 660-watt units are the most popular. Most only use a fraction of that energy during actual operation, especially if you use automatic shutoff, “eco” cooling settings, and other features that reduce power consumption. Measure the area that you want to cool carefully, so you get the right size machine. Choose one with a high Energy Efficiency Rating to help reduce your environmental footprint while you stay cool.

Featured Image Credit: ND700, Shutterstock


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