Measure the time the power is used with a stopwatch.
Convert the time to hours. If your time is in minutes, divide the number of minutes by 60. For example, if you used the power for 180 minutes, divide 180 by 60 to get 3 hours. If you use an appliance for days, multiply the number of days by 24 to convert to hours.
Divide 1,000 kWh by the number of hours used to find the kilowatts. For example, if the device ran for 20 hours, divide 1,000 kWh by 20 hours to get 50 kW.