How Many Watts Does a Portable AC Use?

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Updated January 16, 2023

If you want the best air conditioners to keep your house cool, you need to know what ratings and numbers to look for. A portable unit will often list its BTUs and tonnage. But determining watts of energy is a little trickier. Instead of listing base wattage, most units list an EER rating. Understanding how many watts a portable air conditioner uses can help you estimate your operating cost.


  • The Energy Efficiency Ratio (EER) determines the connection between watts per hour and British Thermal Units (BTUs).
  • The higher the EER rating, the better.
  • Different manufacturers and units use different watts per hour.

Size and Wattage of Air Conditioner Units

Many factors go into buying good portable AC units. And if you have one, knowing how often to service an air conditioner keeps a good unit running. If you’re still in the market, however, you’ll want a unit that can remove the right BTUs of heat per hour for your space. So, you’ll need to know how many BTUs do you need for an air conditioner. To get a good measure of this you will need to know how many tons of air conditioning do I need. For that, you’ll need a unit’s BTU number. If you don’t know where to find the BTU on an air conditioner, we have helpful articles that can assist you. When you have both of those, along with the EER, you can now determine the watts of electricity a unit will use. And if you wish to learn about a different type of cooling system, you can check out our comparison of a chiller vs an air conditioner. However, if you need a high-BTU portable AC, check out our LG LP1415WXRSM Portable Wi-Fi Air Conditioner review.

Insider Tip

Knowing the BTUs to Kilowatt formula can help you find the right unit for you among all the various air conditioner sizes.


As a rule of thumb, the watts per hour of an AC unit multiplied by the EER should equal the BTU of the unit. To turn the equation around and find out the number of watts a unit uses, divide the BTU by the EER. This will give you the average watts the portable unit uses.


If you want to cool the entire house, repeat this process for each unit you may purchase. Not all types of air conditioners can cool all spaces, so make sure each unit is suited to the room it is intended for. Additionally, if you purchase a mobile unit, you’ll want to know how often you need to drain a portable air conditioner to keep it running smoothly.


Compare the total watts per hour from your combined AC units to the watts per hour your household currently uses. This will give you a rough estimate of how much the new units will affect energy costs.


The more hours per day you run an AC unit, the higher your energy costs will be. Similarly, check your utility bills to find out your cents per hour rate so you can get a rough idea of how much the unit’s power consumption per hour will cost.


How much power does a central air conditioner use?

The watts per hour are dedicated to a central air conditioning system depending on your local climate. Generally speaking, central AC uses roughly 3,000 to 3,500 watts each hour. Warmer climates may have a wider range of AC watts because the air is warmer but the home’s insulation may be more efficient and more easily contain cold air so they can use a fan-only mode.

Do air conditioners use a lot of electricity?

Whether you opt for central, portable, or window air conditioners, it is very likely that your cooling units will use more energy than anything else in your home. Even energy-efficient models are likely to consume much more electricity than other appliances. Looking for an Energy Star appliance may help reduce an AC unit’s power drain, however.

Does the EER rating really help me save money?

The efficiency rating will save you money. Higher air conditioner efficiency means lower power consumption which lowers the average operating cost.

Where to find watt ratings?

You can often find the air conditioner wattage in the manual that comes with a newly purchased unit. The information may also be on the manufacturer’s website or may be provided on request to aid you in making an informed decision.

STAT: In warmer climates such as California, 30% of the peak electricity demand during the summer months is created by air conditioning use. (source)

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