Convert Btu to Watts (5,000 – 60,000 Btu Air Conditioner Watts)

Air conditioners use less than 400 watts to more than 16,000 watts – a large range of electricity use. Window air conditioners, portable air conditioner, mini split and standard split system central air conditioners all use a different range of watts (or kilowatts, once the usage is about 1,000 watts).

Consumers want to know how many watts air conditioners use as they consider which one to buy. Watts equals energy costs, and the more efficient the unit, the lower your electricity will be.

This AC watts guide includes a calculator – plug in the BTU capacity of your air conditioner and its EER rating, and the calculator will convert the values to watts. The formula used in the calculator is BTU/EER=Watts. Divide watts by 1,000 to get the kW or kilowatts.

Here is our “Convert BTU to Watts” Calculator which can help you get the result quickly.

BTU to Watts Calculator

Here is the BTU to Watts chart for some key EER ratings:

How Many Watts Does A Poratable / Window Air Conditioner Use?

Window/Portable/Mini Split AC Capacity (BTU)Watts
5,000 BTU 385-550
6,000 BTU 462-670
8,000 BTU 640-950
9,000 BTU 720-1,050
10,000 BTU 800-1,170
13,500 BTU 1,230-1,700
15,000 BTU 1,360-1,875

How Many Watts Does A 1 – 5 Ton Air Conditioner Use?

Central AC Capacity (Tonnage)Watts
1.5 ton 1,150-1,470
2 ton 1,520-1,960
2.5 ton 1,900-2,450
3 ton 2,300-2,950
3.5 ton 2,650-3,400
4 ton 3,050-3,900
5 ton 3,800-4,900

How Many Watts Do Air Conditioners Use?

TypeBTU RangeRunning WattsStarting Watts
Window5,000-24,000 BTU385-1,715 watts1,000-5,000 watts
Portable8,000-14,000 BTU640-1,700 watts1,900-5,000 watts
Mini Split6,000-48,000 BTU462-3,429 watts1,400-10,000 watts
Central AC18,000-60,000 BTU1,142-4,897 watts3,000-12,000 watts

How many watts an air conditioner uses is impacted by two key factors, or as it is technically referred to, how many watts it draws.

AC Size – The more BTUs of heat-moving capacity the AC has, generally the more watts it will use. It’s obvious, for example, that a 5,000 BTU window air conditioner uses less energy than a 14,000 BTU portable air conditioner and a 48,000 BTU central AC.

AC Efficiency – Air conditioners vary widely in how efficiently they use electricity to move heat. Generally speaking, mini split and central air conditioners, especially the most efficient of them, use less power per BTU. Also, newer air conditioners of all types are more efficient than older ones.

Did you know? Your air conditioner probably requires more watts to start than it does to run. A lot more, in most cases. For example, according to this generator dealer, a 24,000 BTU AC needs 6,000 watts (6kW) to start but just 2,000 (2kW) to run. It’s about 3 times more for most AC sizes; Not exactly 3 times as much, but that’s a pretty close figure.

Where to Find Watts Ratings

There are a couple places to look. And we show an example from Rheem. Now, it’s likely you have another brand, but the example gives steps for finding the information for most brands in the same way.

The papers that came with the AC – In the papers, you should find a specification sheet, or it could be a page in the manual. It will list a range of specifications including watts or kilowatts depending on the size of the unit. Remember that 1 kW = 1,000 Watts.

Online – The product’s model number should be listed on a small label or plate on the unit. Search the model unit. On the product page, look for documents and choose Specifications. For example, if you have an LG LW8017ERSM window air conditioner, look for the Specifications or Specs tab and select it.

Then choose Download Spec Sheet.

When you do, you’ll see a section called Electrical Ratings. As you can see, this window AC uses 660 watts of electricity to run.

Note of Caution – The performance of an air conditioning listed in watts or kilowatts is not how much it uses! For example, Rheem central AC uses about 4,000 watts, but it can move up to the equivalent of 17,700 watts of energy per hour. They are really two different ratings. This can be confusing if you’re not aware it is kW performance and not usage. That’s the great thing about air conditioners – they use refrigerant to multiply their performance power.

Efficiency Makes a Big Difference!

Use our BTU / EER Watts calculator to explore efficiency


Many air conditioners are rated by SEER, the seasonal energy efficiency ratio, rather than EER, the energy efficiency ratio.

If you know the SEER of your unit but not the EER, use our Convert SEER to EER Calculator, and then come back to this page of PickHVAC to determine the watts your air conditioner is using.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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