Calculating Kilowatts Using BTU

Before you commit to a particular AC unit, you may want to know how much electricity it may consume to cool your home. That way, you get an idea of how it will influence your utility costs. BTUs, when converted to kilowatts and kilowatt-hours, can help you figure that out.

First, a quick explainer: A kilowatt is 1,000 watts, which is a measurement of power. A kilowatt hour measures the amount of energy needed to run an appliance, tool or machine for one hour. When it comes to your air conditioning, a kilowatt hour tells you how much energy your AC is using, which could be instrumental in helping you decide what kind of unit to buy.

To convert BTUs to kilowatts, take your BTUs and multiply them by 0.000293 — the amount of kilowatt-hours in one BTU. For example, if you’re looking for an air conditioner with 18,000 BTU, you’d get 5.27 kilowatts, or 5,270 watts. Let’s say your AC runs for four hours a day. Within that period, your air conditioner would use 21.08 kilowatt hours (5.27 kilowatts x 4 hours).

18,000 BTU x 0.000293 = 5.27 kilowatts

5.27 kilowatts x 4 hours a day = 21.08 kilowatt hours for your air conditioner

If you want to determine your estimated energy costs, multiply your kilowatt hours (21.08, in this case) by 30 for 30 days in a month. That gives you 632 kilowatt hours per month. You’ll need to multiply this figure by the electricity rate you’re charged each month. As of May 2021, the average electricity rate in the U.S. was 13.71 cents per kilowatt hour, according to the U.S. Energy Information Administration. By multiplying your electricity rate by your kilowatt-hours, you can determine your energy costs:

21.08 kilowatts x 30 days in a month = 632 kilowatt-hours per month

632 kilowatt-hours x 0.13 cents per kilowatt hour = $86.70

We know that’s a lot of number-crunching. But hopefully those calculations can help you make a more informed purchasing decision.