How Much Does Air Conditioners Cost To Run? (With Calculator)

How much electricity does a room AC use? And how much does it cost to run a room AC?

The average window or portable AC costs about 46 cents per hour ($0.46/hour) to run based on using about 3.5 kilowatts/hour.

However, window air conditioner size and the cost of electricity are both important factors. A small AC where electricity is cheap costs about 15 cents/hour; a large AC where electricity is expensive can cost around $1.50 per hour.

Monthly Cost: The cost to run an AC, window AC or portable AC in summer is:

  • Low – $54/month
  • Average – $96/month
  • High – $148/month

We will help you understand the cost of running your air conditioner in your state. That’s what you’re here to find out – and we Pick HVAC has answers.

This guide gives you complete information including a calculator to determine the answer to the Q: How much does it cost to run a window AC or portable AC per hour, per day and per month. As you know, this site is your go-to choice for accurate answers to your HVAC questions and when you’re searching for the most cost-effective HVAC products for your purposes.

The first key is to know the cost of electricity.

The Cost of Electricity 10 to 30 Cents per Kilowatt

According to the EIA (Energy Information Administration), the current average cost per kilowatt is 13 cents, or $0.13, for residential customers – for your home or apartment.

Read This First: Don’t Use 13 cents/kilowatt without checking!!!

Depending on where you live, the cost can be less than 10 cents and more than 30 cents per kilowatt. That’s a huge range.

Do This First: You can find your cost of electricity on your energy bill or bills, the energy company website or on the EIA site.

Room AC Electricity Cost Calculator

OK, with that out of the way, here is the electricity cost calculator. We use a simple formula that considers the average number of watts of electricity used by ACs of various BTU sizes. In other words, you don’t need to know the unit’s wattage/hour.

AC Cost to Run

Below our AC cost to run calculator, we’ll discuss how to reduce energy use, improve energy efficiency and answer FAQs.

  • BTUs: Just plug in the numbers once you know the BTUs of the AC you have or intend to buy.
  • Energy Cost: And you must know the cost of electricity you’re paying. The EIA (Energy Information Administration) page gives average costs per state, but to be more precise, try to find and use the exact cost you pay.

Cost Tip: In summer, some energy companies charge a premium for electricity during the peak hours of the day. So, since you’ll be running your AC during those hours (they are usually about 10am to 7pm), then find that amount too.

How to Use an AC Cost Calculator

Follow these easy steps to determine how much it will cost to run a room AC.

1. Enter the AC Capacity

*I Have an AC: Find the BTU rating on a metal tag on the AC or in the owner’s manual. Or search the brand and model number, find the product page, and it will give you the BTU rating. For example, see this product page for the LG LW1221HRSM window air conditioner. The number of BTUs is clearly stated as 12,000.

*I Don’t have an AC: If you’re considering what size AC to buy, know how many square feet you need to cool. Measure length x width for the room’s square feet.

  • Window AC: 1000 BTU per about 40-45 square feet for maximum cooling. So, a 6,000 BTU AC will cool up to about 240 square feet. A 10,000 BTU unit will cool up to 400 square feet, and maybe a little more. An 18,000 BTU window AC can cool about 800 square feet – possibly a little more.
  • Portable AC: These room ACs don’t have the energy efficiency of a window air conditioner. So, expect them to cool about 25 square feet per 1,000 BTU if using the ASHRAE rating or 40 if using the SACC rating. See the manual or product page for the information.

2. Enter the Cost of Electricity

Check your energy bill or the provider’s website for the exact amount you’re being billed for the electricity wattage – listed as kW or kilowatt.

3. Choose your Time Period

1 Hour, 12 Hours, 24 Hours or the average Monthly usage.

Note on Monthly: Choose Monthly only if you run the AC all day, every day – 24 hours per day for 30 days! Most people run their AC 4-10 hours per day.

4. View the Cost in the Box

Our AC Cost to Run calculator does the math. View the Cost in the Box at the bottom.

AC Cost to Run Examples

Here are average costs to run the most common window air conditioner sizes at different electricity cost levels. We used our air conditioner cost calculator to determine them.

Costs are per hour:

Kilowatt Cost = $0.10

  • 6,000 BTU: $0.18
  • 10,000 BTU: $0.29
  • 14,000 BTU: $0.41
  • 18,000 BTU: $0.53
  • 24,000 BTU: $0.70

Kilowatt Cost = $0.13 (U.S. Average)

  • 6,000 BTU: $0.23
  • 10,000 BTU: $0.38
  • 14,000 BTU: $0.53
  • 18,000 BTU: $0.69
  • 24,000 BTU: $0.91

Kilowatt Cost = $0.20

  • 6,000 BTU: $0.35
  • 10,000 BTU: $0.59
  • 14,000 BTU: $0.81
  • 18,000 BTU: $1.05
  • 24,000 BTU: $1.41

Kilowatt Cost = $0.25

  • 6,000 BTU: $0.44
  • 10,000 BTU: $0.73
  • 14,000 BTU: $1.03
  • 18,000 BTU: $1.32
  • 24,000 BTU: $1.76

The following tables use the US Average rate of $0.13 / 13 cents per kilowatt (kW). Note that most states do not have average rates, so check your electricity bill or utility company website to find out exactly what you pay per kW of energy.

Common Portable AC SizesAverage Cost Per Hour (1)
5,000 btu portable air conditionerN/A - There are no portable ACs this size
6,000 btu portable air conditionerN/A - There are no portable ACs this size
8,000 btu portable air conditioner$0.30 (30 cents)/hour
10,000 btu portable air conditioner$0.38/hour
12,000 btu portable air conditioner$0.46/hour
14,000 btu portable air conditioner$0.53/hour
18,000 btu portable air conditionerN/A - There are no portable ACs this size
(1) Based on US Average Electricity Cost of 13 cents per kW - Cost Varies in Each State
Common Window Air Conditioner SizesAverage Cost Per Hour (1)
5,000 btu window ac$0.19 (19 cents)/hour
6,000 btu window ac$0.23/hour
8,000 btu window ac$0.30/hour
10,000 btu window ac$0.38/hour
12,000 btu window ac$0.46/hour
15,000 btu window ac$0.57/hour
18,000 btu window ac$0.69/hour
24,000 btu window ac$1111.11)
(1) Based on US Average Electricity Cost of 13 cents per kW - Cost Varies in Each State

Note: If you do the math, you’ll see the cost is about 3.8 cents per 1,000 BTUs of cooling power.

AC Operating Cost Factors

We’ve covered most of the factors in the calculator.

  • AC Size – Window air conditioners are available from 5,000 BTU to about 24,000 but. Portable air conditioners come in 10,000 to 14,000 BTU sizes, or when adjusted for the newer SACC rating, about 5,500 to 7,700 BTU.
  • Cost of Electricity – See your energy bill.
  • Run Time – Your climate, how much insulation your home has and your preferred indoor temperature all affect Run Time.

There are a few other factors.

  • Energy Efficiency of the AC: The more efficient the unit in terms of EER, CEER or SEER, the less it will cost to run.
  • 115 vs 230 Volt ACs: A 230-volt unit uses more energy, but it might cool more quickly too. Smaller units are 115 volt. Midsize window units come in both options. Large window ACs are 230 volt models.

Energy Saving Tips When Running AC

You can’t change your cost of electricity, but there are ways to get better energy efficiency from your unit.

Choose an Energy Star AC

There are many Energy Star certified window air conditioners. No portable units meet Energy Star criteria.

Upgrade your Home or Room Insulation


Make sure there is the appropriate amount of attic insulation. Most energy experts recommend at least R-38 for most climates, and even higher in very hot climates.

Add weatherstripping around all doors and windows

Buy the Right Size AC

If you buy one that is too large for the room, you’ll waste energy. Plus, the room might end up being too chilly. The AC won’t optimize dehumidification either, so the air might feel cool and humid.

Cost to Run AC – FAQs

Here are common questions with answers from our HVAC professionals.

How much does it cost to run a portable or window AC per hour for heating?

If you have an AC with heat – and there are a few – cost might be higher than when in AC mode. Based on the wattage of most ACs with a heat element, the average cost is around $0.80, or 80 cents, per hour.

What costs more to run an ac or dehumidifier?

The average cost to run a dehumidifier is lower than the cost to run an air conditioner. This is because dehumidifier fans are not usually as powerful.

How much does ac cost per month in an apartment?

The size of your apartment will determine the size of the AC, how long it needs to run and other cost factors such as how long the AC runs each day.

These prices are based on an average electricity cost of 13 cents per kilowatt and running the AC for 8 hours per day:

  • 400 square foot apartment: $66
  • 600 square foot apartment: $107
  • 800 square foot apartment: $144
  • 1,000 square foot apartment: $195

What is the cheapest way to run an air conditioner ?

First, buy an Energy Star certified room AC that is the right size for the space.

Then, use Sleep Mode and Energy Saver mode when the AC has been on for a few hours and the room temperature is where you want it to be.

Finally, use a timer or WiFi app to start the AC an hour before you want to use the room. This is the cheapest way to run an air conditioner rather than running it all day – see the next Q.

Is it OK for AC to run all day?

If your climate is hot, hot, hot from just after sun-up into the evening, you might have to run it all day. But only if you’re using the room.

Otherwise, as we said above, buy an AC with a timer or WiFi app, so you can easily control when it starts and stops when you’re not there.

In short, it isn’t OK to run the AC all day if nobody is in the room and you want to reduce energy use.

Is it cheaper to keep the AC on auto?

Yes, typically it is cheaper to run an AC in Auto Mode. The AC’s digital board will determine the right cooling level and fan speed, and this will use less energy than if the AC is running on maximum power all the time.

So, yet, it is cheaper to keep the AC on Auto.

At what temperature AC consumes less power?

Obviously, when the AC thermostat setpoint is reached, known as when the thermostat is satisfied, the compressor will turn off and the AC consumes less power.

In terms of temperature setting, the higher you set the thermostat, the less power the AC consumes. We recommend a thermostat setting of 75F to 78F vs. 70 or 74, if you want the AC to consume less power.

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