There are times it is important to know how many kilowatts (kW) or watts a piece of heating or cooling equipment is using when all you know is the BTU output of the unit.
The conversion from BTU to kW is really quite straightforward depending on the type of equipment you own. We have two calculators on this page, and they are best used with different types of equipment.
How to Convert BTU to kW
BTU is used by U.S. manufacturers and in the U.K. too. Most European manufacturers list the efficiency of their units in kW. If you’re looking at a unit that gives you information you’re not used to, converting it to the rating you are familiar with let’s you know its heating or cooling capacity.
A BTU, or British Thermal Unit, is a measure of heat energy. When discussing resistance heating equipment, its BTU rating refers to how much heat it makes per hour, so properly written as BTU/h.
For air conditioning equipment and heat pumps, its BTU/h rating is how much heat it moves per hour. An air conditioner captures heat indoors and moves it outdoors. A heat pump absorbs heat from outdoors and moves it inside.
Direct Equivalent BTU to kW Calculator (Heating)
The first BTU to kW calculator gives you the direct equivalent: BTUs = X kW. It’s the right calculator to use when you want to convert an electric resistance appliance to kilowatts (watts x 1,000) when you know the BTUs. Electric resistance heat appliances include electric furnaces and space heaters.
The equation used is the universal conversion : 1 BTU/h = 0.00029307107 kW. Mathematicians might also write this as 1 BTU = 2.9307107 x 10 to the -4 power.
Another way to put this is that 1kW = 3,412 BTU/h.
The reason for the direct equivalent calculation is that the efficiency of the equipment isn’t factored when evaluating direct resistance heat appliances.
Air Conditioner BTU to kW Calculator (AC/Heat Pump)
The second calculator does factor in efficiency, which is vital when evaluating an air conditioner, whether a central or mini split AC, window air conditioner or portable air conditioner, or a heat pump.
It uses the formula BTU/EER = watts, which the calculator then divides by 1,000 to give you kilowatts.
For example, if you have a 24,000 BTU AC and it’s EER rating is 8, our calculator gives an answer of 3kW.
If its EER rating is 10, then it uses only 2.4 kW of energy per hour. That’s an energy savings of about 20%, and that adds up over the course of a heating or air conditioning season.
Why does efficiency affect the BTU to kW ratio? Because the more efficient the unit is, the less energy it takes to do the same work. Remember that air conditioners and heat pumps just move heat from one place to another. Refrigerant absorbs the heat energy, and it is circulated to where you want it to go – outside in warm weather and inside in cold.
Did you know? We’ve completed a guide called How Many Watts Do 5,000 – 60,000 BTU Air Conditioners Use? It also has a conversion calculator plus a chart showing the BTU ranges for most size residential ACs of all types from 5K to 60K.
Where to Find the EER Rating
We’re often asked, “what is the EER rating of my AC” or “how can I find the EER rating?”
- On the Unit: It’s possible it is listed right on the unit – look for a metal label with the model number and other details. It might list its EER rating too.
- In the Manual: The EER rating might be on the front cover. If not, the manual should have a specification page showing its efficiency rating, how much energy it uses and other details.
- Online: Search your unit online, and go to its product page. Look for a tab called Specs or Specifications. Some pages have a tab or button called Documents where you can find the Spec Sheet. For example, let’s say you own an LG LW8019ER window AC. Find its product page by searching online. Then, scroll down to the Specs tab and select it. Finally, choose Download Spec Sheet, and the EER rating appears at the top.
What if I Know SEER But Not EER? Or CEER?
No problem. This PickHVAC guide covers that topic and has a calculator too. Plug in the SEER of the AC, and you’ll be given its EER rating.
And if all you have is CEER, we can help there too with this page. Unfortunately, there currently isn’t a means of converting CEER to EER.
And what does EER stand for and what does it mean? This page explains what EER is and how it is determined.
If you have a space heater or electric furnace, use the top calculator. If you want to know how much energy your air conditioner is using, the second calculator is the right one because it factors efficiency.
For either, plug in the values, and the conversion is automatically made.