Estimating Air Conditioning Costs: A Guide

Many homeowners wish they could know just how much money running their air conditioner costs them. Calculating the exact amount running an air conditioner costs depends on many factors, including your home’s size and the efficiency of your unit. There is, however, a simple method for estimating cost.

Key Terms for Estimating A/C Costs

To understand the information in this method of estimating the cost of running an air conditioning unit, a homeowner will need to know a few key terms:

  • An ampere (amp) measures how much electricity is flowing through something.
  • Watts measure the amount of energy transferred over time. One thousand watts is a kilowatt.
  • Volts measure the electrical potential between two points on a wire.
  • Kilowatt-Hour. A kilowatt-hour measures the number of kilowatts used in one hour. This is the basis for electricity bills. The amount of kilowatt-hours used during the month will determine a home’s electricity bill.

Estimating Air Conditioner Operating Cost

With a basic understanding of the terms above, it is possible to find an estimate of how much an air conditioner costs to run for a month. These are the steps to the estimation process:

  1. Find out the amount of amps drawn by the air conditioner. This will vary depending upon the unit’s seasonal energy efficiency ratio (SEER) rating, but a quick estimate is:
    • 2-ton unit – 15 amps.
    • 3-ton unit – 18 amps.
    • 4-ton unit – 21 amps.
  2. Calculate watt and kilowatt usage. Central A/C units use power from a 240-volt outlet. Multiply the amount of amps the unit draws by 240 (110 for window A/C units) to find the number of watts the unit uses. Divide that number by 1,000 to find the number of kilowatt-hours the unit uses.

    21 X 24 = 5040

    5040 ÷ 1000 = 5.04

  3. Multiply the number of kilowatt-hours found above by 24 to see how many the unit uses in a day, then again by the number of days in the month to find out how many kilowatt-hours it uses for the month. Finally, look up the price charged for each kilowatt-hour by your electrical company, and multiply this by the kilowatt-hours found above. (For this equation, we will use 15 cents per kilowatt-hour.)

    5.04 X 24 = 120.96

    120.96 X 30 = 3628.8

    3628.8 X $.15 = $544.32

    Now, this number will probably be much, much higher than a homeowner’s entire energy bill for the month because this would be how much it costs to run the unit continuously.

  4. Use the outside temperature to find how much the unit runs. Another rough estimate can be used to find out how often an A/C unit runs.
    • At 110 degrees – the unit runs 80% of the time, or.8.
    • 100 degrees – .4.
    • 90 – .3.
    • 80 – .25.

    Multiple the dollar amount from step three by the multiplier determined by the outside temperature to discover the final estimated cost of running an A/C unit for a month.

    5544.32 X .3 = $163.30

  5. Once you figure out the cost of running your AC unit, it will be easier to create a monthly budget for your cooling costs. If you find your air conditioning costs are too high, there are many ways to reduce these costs. Contact us for more information on how to save money on your monthly cooling bills.