FreeHVACCalculators

Start here

Menu

Electric Meter Watts Calculator

Find out how much power your home — or one appliance like an air conditioner — is drawing right now, by timing the meter’s disk or pulse light.

Method reviewed October 26, 2026. Version 1.0.0. How it works

Your inputs

Printed on the meter face, e.g. “Kh 7.2”.

Seconds.

Measure once with the appliance off and enter it to isolate the appliance.

Result

Total power at the meter
2,160W

2,160 W at the meter.

  • Count several revolutions or pulses for a steadier reading, and keep other large loads off during the test.
Appliance (total minus baseline)
2,160W
Heat equivalent of the total
7,370BTU/h
Show the working
  1. W = Kh (Wh per revolution) × revolutions × 3,600 s/h ÷ seconds
    7.2 × 1 × 3,600 ÷ 12 = 2,160 W

How to do it

  • Find the meter constant Kh on the meter face: the watt-hours per revolution of the disk, or per pulse of the test light on many electronic meters.
  • Time one or more revolutions (or pulses) with a stopwatch.
  • Watts = Kh × revolutions × 3,600 ÷ seconds.

To isolate one appliance, measure once with it off and once with it on, and subtract.

Getting a good reading

Turn off other large loads, time several revolutions for a steadier reading, and let a heat pump or air conditioner run for a few minutes before measuring. If your meter shows a multiplier or a different pulse value, check with your utility.

Worked example

These are the example values the calculator opens with, and the result the engine calculates for them.

Inputs

Meter constant Kh (watt-hours per revolution or pulse)
7.2
Revolutions or pulses counted
1
Time for those revolutions
12
Power with the appliance off (optional)
0 W

Result

Total power at the meter
2,160 W
Appliance (total minus baseline)
2,160 W
Heat equivalent of the total
7,370 BTU/h

2,160 W at the meter.

Assumptions

  • Kh is the watt-hours registered per disk revolution (or per test pulse on electronic meters).

Limitations

  • Some meters use a multiplier or different pulse value; check with your utility if the result looks wrong.

Frequently asked questions

Where is Kh on my meter?

It is printed on the meter face, often labelled “Kh”, for example “Kh 7.2”. Electronic meters may state the Wh value of each test pulse.

How do I find my AC’s power use?

Time the meter with the AC off, then with it running steadily. The difference in watts is the AC’s draw.

How do I turn watts into cost?

Multiply kilowatts by hours of use and your price per kWh, or use the AC Electricity Cost Calculator.

Sources

  1. Determining kW Use — Fundamentals of Electricity (utility customer guidance) — Minnesota Power, via Apogee Interactive. kW = revolutions ÷ seconds × 3.6 × Kh, where Kh is the watt-hours per disk revolution printed on the meter.

Spotted an error? Report a problem with this calculator — see our corrections policy.