Window AC Unit Wattage: How Much Power Does a Window AC Use?

Finding out your window AC unit wattage isn’t difficult, but if you’d also like to know how much the electricity cost would be, read this guide for more details.

Are you thinking of getting a window AC unit for your home? Do you live in an area where hot weather is an everyday occurrence and you need a quick and easy solution to that? Because you are an environmentally and pocket-conscious person, before you decide on a window AC model, you want to make sure that you know all the facts and figures, including your window AC unit wattage. To find out everything you need to know about how much energy your window AC unit will spend, keep on reading.

How Much Power Does a Window AC Use?

The amount of power a window AC unit uses depends on many factors, which we will address later in this article. There are different types of window AC units, different brands, and more importantly, different energy requirements based on the size of the unit. For example, on average, a 5000 BTU air conditioner will spend about 550 watts of electricity. The higher the BTU count, the higher the watts usage. In order to have a more specific perspective on how much power a window AC unit uses, we can learn how to calculate the cost of running one per day or per hour.

How to Calculate the Cost of Running a Window AC


If you’ve purchased a window AC unit, or are considering one, and you want to find out how much it’s going to cost you to run it per hour/day, there’s a very simple formula to that. All you need is to gather three simple numbers and do the calculation. Follow the steps below.

Find out how much you pay per kilowatt/hour (KWh)

The first thing you need to know in order to calculate the cost of running your window AC unit is to find out how much you pay per kilowatt/hour (KWh). It differs depending on where you live, but the US average is $0.13. In order to find out this number, you can check your electricity bill or you can check the website of your electricity company.

Find out your window AC electricity usage in watts

This figure will vary according to the window AC model and size; finding it out is as simple as checking the appliance’s manual and specifications. Once you found the watts, you are ready for the next step. 

Do the calculation

So now you have three figures: the amount you pay per kilowatt/hour, the watts usage of your window AC unit, and the number of hours you plan on using it per day. Now it’s time to do some basic calculations with these numbers. 

  1. Multiply the watts usage of the window AC unit by one hour. 
  2. Then, divide the above result (watts) by “1000” to obtain kilowatt/hour (KWh). 
  3. Finally, multiply the KWh by the price of kilowatt per hour. If you use your unit for 8 hours a day, then you want to multiply that number by 8 to figure out your daily cost. Once you have your daily cost, you can easily multiply by 7 to find out your weekly cost or by 30 for your monthly cost.

To make this easier we can use the example of a window AC unit that uses 750 watts and assuming one pays $0.13 KWh:

  1. 750 watts x 1 = 750
  2. 750 / 1000 = 0.75 (KWh)
  3. 0.75 x 0.13 ($) = 0.097 ($/h)

In order to find out the daily cost of operation then you multiply this result by 8.

What Factors Impact Your Energy Use?


When considering the energy use of a window AC unit, a number of factors will impact this energy consumption. Using any home appliance, including a window AC unit, has its own dos and don’ts to use efficiently and effectively. There are three factors that could make your window AC unit spend more energy than it should.

The window AC unit efficiency

Generally, window AC units have a sticker with an energy guide. The ratios used to indicate their efficiency are the Energy Efficiency Ratio (EER) and the Seasonal Energy Efficiency Ratio (SEER). The higher the EER or SEER number, the more efficient the AC unit is and the less electricity it will use.

Indoor and outdoor temperature

The way the window AC unit functions is that when you set it to a temperature, it will work until it reaches that temperature; at that point, it will turn off, and only the fan will blow. This means that the lower you set the temperature, the more the unit will have to work to reach that temperature, and therefore, it will use more electricity.

Also, when the temperature is extremely hot outside, this will make it more difficult for the window AC unit to do its job efficiently. It will have to work much harder to reach the temperature you set. When this happens, the cycle will not turn off as we said above; instead, the unit will keep running to beat the hot air outside to reach the temperature. So if you live in a place where the weather is often way too hot, then be prepared to pay more for running a window AC unit.

Open windows and doors

The number one thing you need to remember in order for your AC unit to run as efficiently as possible and not spend too much energy is to keep doors closed where the AC unit is running. If there are windows and doors constantly open, the window AC unit will work a lot harder to cool the area and thus spend a lot more energy than needed. 

Window AC vs. Portable AC


You may wonder if purchasing a window AC unit or a portable AC unit would be more energy efficient. Both of these models do their respective jobs in terms of cooling a specific area. Portable AC units are less expensive and easier to install and move around to whichever room you’d like. However, window AC units are actually more energy-efficient than portable AC units. You can get a more powerful experience with low BTU, whereas a portable one requires more energy to cool an area. So if you want to purchase something that will cool your home and won’t spend too much energy at the same time, then you should go with a window AC unit. 


Figuring out the energy use and the electricity cost of a window AC unit may seem a little daunting, but if you are concerned about your bills, you will definitely want to do that. If you live in a very hot place, having an AC is not a commodity, it’s a need. Your options are plenty. And if you are concerned about the environment, following some of the tips above for a more energy-efficient use of the unit will also diminish the impact on the environment. 

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