Are you thinking of buying a window air conditioner but not sure if it’s worth the money?

Do you want to know how much a window AC unit will actually cost you each month before you make the investment?

If so, this free guide can help.

Not only will we go over how much electricity does a window AC unit use, but we’ll also reveal how you can figure out the cost it takes to run a window air conditioner each hour.

By the end of this post, you’ll have everything you need to make a well-informed buying decision on a new window air conditioning unit.

And once you’re finished reading, you’ll also want to jump over to our guide on the top rated window air conditioners where we go into more detail on how to pick the best device for your needs and budget.

How Much Electricity Does a Window AC Use?

On average, a window AC unit can use between 500 to 1,500 watts of electricity to run. A midsize window air conditioner that uses 900 watts of electricity will consume approximately 200 kilowatt-hours of electricity each month if operated 8 hours per day.

Window AC Unit (BTU)Estimated Watts
5,000 BTU Window Air Conditioner550 Watts of electricity
8,000 BTU Window Air Conditioner660 Watts of electricity
10,000 BTU Window Air Conditioner900 Watts of electricity
12,000 BTU Window Air Conditioner1,100 Watts of electricity
15,000 BTU Window Air Conditioner1,500 Watts of electricity

How Many Watts Does an Air Conditioner Use?

Air Conditioner (BTU)Estimated Watts
Small Window AC Unit (5,000 BTU)550 Watts of electricity
Medium Window AC Unit (8,000 BTU)660 Watts of electricity
Large Window AC Unit (15,000 BTU)1,500 Watts of electricity
Small Central Air Conditioner (10,000 BTU)3,000 Watts of electricity
Medium Central Air Conditioner (14,000 BTU)4,000 Watts of electricity
Large Central Air Conditioner (18,000 BTU)5,000 Watts of electricity

The table above shows you the average of how many watts an air conditioner uses based on the type (window vs central air) and the BTU rating.

How Much Power Do Air Conditioners Use?

If you want to get very specific on the power consumption of watts on an air conditioner, then the follow table can help.

The relationship between BTU and power in wattage for an air conditioner is determined by the Energy Efficiency Ratio (EER). The EER rating can range between 8 EER to 18 EER depending on the type of air conditioner being measured. (Central air conditioners can have the highest EER ratings.)

If an air conditioner has a low EER rating, then it will use more watts to power the unit. If it has a high EER rating, then it will use less wattage and power consumption.

In the table below, we’ve given you the average watts used for air conditioners between 5,000 BTU to 18,000 BTU with an EER range between 8 and 12.

Air Conditioner (BTU)Estimated Watts
How many watts does a 5,000 BTU AC use?417 – 625 Watts
How many watts does a 6,000 BTU AC use?500 – 750 Watts
How many watts does an 8,000 BTU AC use?667 – 1,000 Watts
How many watts does a 10,000 BTU AC use?833 – 1,250 Watts
How many watts does a 12,000 BTU AC use?1,000 – 1,500 Watts
How many watts does a 15,000 BTU AC use?1,250 – 1,875 Watts
How many watts does an 18,000 BTU AC use?1,500 – 2,250 Watts

Air Conditioner Monthly Electricity Use Guide

How much electricity does a window ac use

If you want to figure out how much does it cost to run a window air conditioner, then you’ll need to know two things:

  • The cost your electric company charges per kilowatt-hour (kWh)
  • The amount of power your window air conditioner uses to run (watts)

Once we have those two numbers in hand, we can then use a simple formula to calculate the monthly cost of operating the window AC unit.

We’ll show you how to do all of that in three easy steps.

Step 1: Determine Your Home Electricity Cost (kWh)

Every state, county, and city charges a different rate for the use of electricity.

Take these for example:

  • Residential customers of Appalachian Power in Virginia pay approximately 11.1 cents per kilowatt-hour (kWh) for electricity.
  • People who live in Northern Nevada pay 9.2 cents per kWh while customers in Southern Nevada pay 11.2 cents kWh.
  • Residents in San Francisco, California pay 22.1 cents per kWh.

As you can see, the price per kWh varies widely across the United States; however, the national average is 13 cents per kWh.

To find out what you pay per kWh, all you need to do is look at your most recent electricity bill or go to your electric company’s website to see the posted rate.

Once you have your kWh in hand, you can move on to the next step.

Step 2: Find Your Window Air Conditioner Electricity Usage (Watts)

When you’re shopping for a window air conditioner, you’ll often find the appliance described in British Thermal Units (BTU) and not amperage (or watts).

BTU is an international standard for measuring an air conditioner’s cooling capacity and gives you an idea of how large a room the unit can handle.

For example, a 10,000 BTU window AC unit can cool a room up to 450 square feet (i.e. 20′ x 22′ area).

The problem, however, is that not all air conditioners with a certain BTU rating use the same amount of electricity to power the device.

One 10,000 BTU air conditioner may use 900 watts of electricity while another one uses 1,000 watts. The total watts all depends on how energy efficient the manufacturer made the appliance.

So, how do you find out how many watts does a window AC use?

  • Check the product manual.
  • Look at tech specs on the manufacturer’s (or selling company’s) website

Once you know the wattage used for a particular window air conditioner, you can then combine that number with the price per kWh you pay for electricity at home.

That calculation will tell you how much it will cost you to run the window air conditioner each hour, day, month, and throughout the year.

See all of Amazon's Best Selling Window AC Units

Step 3: Calculate the Electricity and Monthly Cost

Figuring out how many watts does a window air conditioner use and the monthly cost for operating the appliance is actually quite simple.

The formula for determining the hourly cost of operation includes:

  • # of watts x 1 (hour of use) ÷ 1,000 x 0.13 (kWh) = hourly cost of operation

Here’s an example of an air conditioner that uses 550 watts:

  • 550 x 1 ÷ 1,000 x 0.13 (kWh) = $0.071 hourly cost of operation

If that was confusing, here’s a break down of each step of the formula for you:

  • 550 (watts) x 1 (hour) = 550
  • 550 ÷ 1,000 = 0.55
  • 0.55 x $0.13 (kWh) = $0.071

Once you know the hourly cost to run your window AC unit, you can easily find out the total per day, month, and year.

If we assume that you run the unit for eight hours per day, here’s how much electricity it costs to operate a 550-watt window AC unit:

  • $0.071 x 8 (hours per day) = $0.57 per day
  • $0.57 x 7 (days per week) = $4 per week
  • $4 x 4 (weeks per month) = $16 per month
  • $16 x 4 (for the months of June, July, August, and September) = $64 cost per season (or year)

This same formula can be used to figure out how much electricity does a portable AC use.

Average Monthly Window Air Conditioner Electricity Costs

How much does it cost to run a window AC for the average person?

If we take the average of operating the unit for eight hours per day and also use the national kWh rate of $0.13, then you can expect to spend the following amount each month on electricity for these various size window air conditioners.

  • 500 Watt Unit (5,000 BTU) = $15.60 per month
  • 660 Watt Unit (8,000 BTU) = $20.40 per month
  • 900 Watt Unit (10,000 BTU) = $26.40 per month
  • 1,100 Watt Unit (12,000 BTU) = $33.60 per month
  • 1,500 Watt Unit (15,000 BTU) = $46.80 per month

Factors That Impact Your Air Conditioner Energy User Per Hour and Day

In a perfect world, the monthly electricity costs outlined in the previous section would be true for everyone.

However, there are many things that can cause your window air conditioner to cost less or more per month to operate.

Some of those things relate to the appliance itself while others are impacted by things you can’t control, like the outdoor climate.

If you’re spending more or less than you expected to use a window AC unit, here are the factors that may be contributing to this fluctuation.


The classic Energy Efficiency Ratio (EER) and the updated Seasonal Energy Efficiency Ratio (SEER) are both ratios that indicate the efficiency of a window air conditioner unit.

Most every window AC unit and wall AC unit will have a big yellow sticker on it called the “Energy Guide”.

And on that guide, you’ll find an EER or SEER number along with the estimated yearly energy cost to run the appliances.

Examples include:

  • 10 EER
  • 11.9 EER
  • 13.3 SEER
  • 17 SEER

The rule of thumb here is that the lower the EER or SEER number, the more efficient the air conditioner. That equates to less electricity and cost to operate each month.

If the window air conditioner you have uses more watts than a comparable product, then it will have a higher EER or SEER number, and therefore cost more the use.

Indoor Temperature

The temperature you set the window air conditioner at can also impact the amount of electricity the unit uses.

When the cooling cycle kicks on, the appliance uses more energy to chill the room.

Then, when the set temperature is reached, the cooling cycle turns off and only the fan blows⁠—and that uses much less electricity.

If you’re setting the temperature really low, like 62-degrees Fahrenheit, then the unit will take much longer to reach that desired temperature, which increases your electricity costs.

Outdoor Climate

Sometimes when it’s really hot outside, the indoor temperature can’t reach the degree you have the window air conditioner set on.

That’s because the unit has to compete too hard against the ambient hot air.

If that happens, then the window AC unit will continue running at full blast without ever turning off the chill cycle, and that will increase your daily cost to run the unit.

If you live in a very hot climate, you can probably expect to pay more per day to run a window air conditioner.

Open Doors and Windows

If you have a window air conditioner running in a room that has a separate open window or door leading out to the rest of the house, then the unit must work harder to cool the room.

The more sealed the area is, the less your window AC unit has to work because the air-conditioned air is contained. And that reduces your costs to use it.

Window Air Conditioner Filter

Did you know that your window air conditioner has an air filter?

It sure does, and the purpose of the air filter is to keep dust, dirt, and other debris from damaging the internal system.

Unfortunately, the air filter gets clogged easily and if you don’t clean it, the efficiency of your window AC unit can go down.

Check and clean the air filter weekly to maximize your air conditioner’s cooling efficiency and to keep your operating costs low.

Maximizing Your Use of a Window AC Unit

In this post, you learned how much electricity does a window AC use and how much does it cost to run a window AC unit.

And as you discovered, the answers depend on both the efficiency of the appliance and external factors that may be out of your control.

However, one thing you can do to always keep your costs low is to try and only use the air conditioner when it’s really necessary.

Often, people leave a window air conditioner running all day long because they tend to forget about it.

But, taking the simple step of turning it off when you leave the house or only running it in one-hour intervals can help you lower your monthly electricity costs.

Something else you can do is ensure that the window air conditioner is properly sized for the room that you’re using it in.

If the window AC unit is too powerful, the device will kick on and off too much (boosting electricity use) and if it’s too small, the unit will run continually at full blast (also increasing your monthly electricity bill).

To make sure you get a properly sized window AC unit, check out our guide on the top rated window air conditioners. It walks you through the steps of getting the right window AC unit for your needs and budget.

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About David Morrison

David is an Air Quality & Comfort Technician. He has expert knowledge on the technology and design of air purification, air conditioning, and heating systems. His main role is to write content that helps people get the most value out of their air purifiers, air conditioners, and heating units. (See Full Bio)