How Many Watts Do 5,000 – 18,000 BTU Air Conditioners Use? (Answered)

We usually choose an air conditioner based on BTU and room size. However, when we’re trying to estimate energy costs, it’s very useful to know how many watts our particular air conditioner use.

Air conditioner wattage is not the easiest information to come by.

Not knowing how many watts does a 5,000 BTU air conditioner use is actually pretty normal. As far as lowering the air temperature is concerned, you only need to know that it has 5,000 BTU and correctly sized for your room/space.

An average 5,000 BTU air conditioner uses 500W of energy running at full capacity.

You can estimate how many watts does an air conditioner with known capacity (BTU) use pretty well with this AC wattage calculator:

0.00 Watts

Estimated Wattage (Based on 10 EER Rating)

There are 3 ways how to check how many watts does your air conditioner use:

  1. Check the specification sheet for Watts. You’ll find the power or wattage (in Watts) in the same section as amperage (in Ampers) and voltage (in Volts).
  2. Check the specification sheet for Ampers and Volts. The power is simply calculated by multiplying the number of Ampers with the number of Volts (something like 10A * 120V = 1,200W).
  3. Use BTU and EER rating to calculate how much power does your air conditioner use. You can divide the BTU by EER rating (something like 5,000 BTU / 10 EER = 500W).

Below you find a table of how many watts do different air conditioners – from 5,000 BTU to 18,000 BTU – use.

A rule of thumb to estimate how many watts of energy different air conditioners use is to take the BTU number and divide it by 10. That’s how you can easily estimate that 5,000 BTU AC units use 500W of energy.

How Much Power Do Air Conditioners Use?

The relationship between BTU and the power (in watts) of an air conditioner is determined by the energy-efficiency EER rating. A good EER rating, for example, is 10. That means that 500W will give us 5,000 BTU of cooling effect. If an air conditioner had a higher EER rating (12, for example), the 500W would give us 6,000 BTU of cooling effect.

In the table above, we’ll assume that the EER rating of all AC units is between 8 and 12. That’s why you’ll see a range for the wattage of air conditioners with the same BTU number:

BTU: Watts:
How many watts does a 5000 BTU AC use? 417 – 625 W
How many watts does a 6000 BTU AC use? 500 – 750 W
How many watts does an 8000 BTU AC use? 667 – 1000 W
How many watts does a 10000 BTU AC use? 833 – 1250 W
How many watts does a 12000 BTU AC use? 1000 – 1500 W
How many watts does a 15000 BTU AC use? 1250 – 1875 W
How many watts does an 18000 BTU AC use? 1500 – 2250 W

As you can see from the table above, a 12,000 BTU air conditioner can use 1500W (8 EER rating) or 1000W (12 EER rating). In short, having a high energy-efficiency air conditioner with a high EER rating pays off. We have gathered the most energy-efficient portable AC units here.

Best Generators For Air Conditioners

If you don’t have a source of electricity readily available, you’ll most probably need a generator to create about:

  • 500 W for 5,000 BTU AC unit.
  • 1,000 W for 10,000 BTU AC unit.
  • 1,500 W for 15,000 BTU AC unit.

We’ve received many questions about which generators are best for a certain capacity of an air conditioner. Here are some of the generators you can use:

All these generations will cover the basic wattage needed to power your air conditioner.

Cost Of Running A 1,000 W Air Conditioner (Estimate)

High wattage air conditioners cost more to run. For example, a 1000W AC unit spends 1 kilowatt-hour of electricity per hour. 1500W unit, for comparison, spends 1.5 kWh of electricity per hour.

Given that an average price of 1 kWh in the US is $0.1319, you can save quite a bit if you invest in an above-average energy-efficient air conditioner.

An average cost of running a 1000W air conditioner is thus $0.1319 per hour. That translates to about $1 for air conditioning if you run such a unit for 8 hours a day.

16 thoughts on “How Many Watts Do 5,000 – 18,000 BTU Air Conditioners Use? (Answered)”

  1. Im worried about start up watts needed to run my 10000 BTU space cooler and refrigerator start up. How big of a generator do I need?

    • Hello Deidre, you would need a generator that can produce up to 1,500W. Green-Power America GPD1500 1500W would be an excellent choice for that.

    • Hello Mogman, you’re exactly right, thank you for the heads-up; we’ve fixed the numbers according to your suggestion.

  2. I have a 1 1/2 HP Submersible pump, Unfortunately, they take surge watts of 7,500 & RUNNING is 2,500 watts. I wish my water well installer would have told me this before he installed. (My aerated compressor system used under 5,000). I just purchased a 8000 watt gas generator as nothing I had could carry the huge load. (Here’s the generic list from EMP (NASA) specialist = Water Well Pumps RATED RUNNING 1,000-2,500, Surge/STARTING 5,600 – 7,500 watts & required voltage 120 or 240

    • Hello Deborah, you’re right, with Submersible pumps, you will have a significantly higher start-up wattage. While a 3000 W generator could run the pump, it can’t be used to start it up. The initial surge can be up to 3x or 4x higher than running wattage.

  3. Hi, i would like to ask if the 3000watts step up & down transformer compatible to insignia portable aircon the capacity is 10,000 BTU ,60Hz, 15A, and 1560W.? Thank u in advance

  4. Thank you so much for this wattage calculator! I don’t think companies get that some (maybe most) customer may want to know the total wattage output before they purchase an item. It’s so true that information about how many watts an item uses is very hard to find.

    Thanks, again!

  5. I have a 9000 btu, 980 watt portable ac with 115 volts and 9.2 amps. Will a 2300watt generator be enough for the surge to start it?

    • Hello Jim, the start wattage should be 2-3 times the max. running wattage. 2300W generator might just cut it. It’s really hard to know for sure, however.

  6. My question is, how big of an generator would I need to run a 13,500 BTU, roof top AC for my RV?
    I currently have a 8,000 BTU stand up AC, with a 1800/2300 generator, and it’s not allowing the compressor to kick on. I was thinking maybe it’s the cable size or length? Thank you for your help!

    • Hello Holly, it depends on the wattage. 13,500 BTU units usually require 1,500W to run; and about 3,000W or 4,000W for the startup. A 5,000W generator should be sufficient; you can run all kinds of other devices that require electricity on that generator.


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