How to Calculate Energy Cost in Kwh


Electrical kilowatt hours are not produced by a random number generator; they are calculated based on electrical watts of energy consumed by the consumer in his home. Understanding a few simple examples of how energy costs are calculated based on kilowatt hours will aid in understanding and managing home energy use.

Things You'll Need

  • Calculator
  • Electric bill

Calculating Energy Cost in kWh

  • Determine the watt rating of a single light bulb in the home and how many hours during the day it is typically on. Use 75 watts as the light bulb rating and six hours per day as an average operating time, for an example.

  • Multiply the six hours per day the light bulb operates by the 75-watt rating of the bulb. The product of 450 is equivalent to 0.450 kilowatt hours per day to operate the 75 watt bulb.

  • Multiply 0.450 watts by 30.5 days to determine the power consumed in an average month. The example calculation renders 13.75 kilowatt hours per month to operate a single 75-watt light bulb for six hours a day.

  • Review the monthly energy bill for the amount charged per kilowatt hour. Use the example of $0.10 per kilowatt hour and multiply this amount by 13.75 kilowatt hours. The result is $1.37 per month to operate a 75-watt light bulb for six hours a day during an average month.

  • Use the same process to calculate the operating cost for other electrical devise and appliance in the home.

Tips & Warnings

  • Most electrical devises and appliances are marked with their typical watt-usage rating. Each device's energy charge can be determined in the same manner.
  • Do not tamper or perform service on live electrical circuits; always isolate or disconnect electrical service in advance.

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