Step 3:
Calculate electrical costs
You now have the monthly use of an appliance in hours. In this step you'll figure out the kilowatthoursthe amount of power that you've used during the month. Then you'll multiplty that figure by the power company's charge per kilowatt hour (or KWH). To find out the rate that you're paying for each kilowatthour, look at your electric bill or call the electric company.
For each item on your list, you'll need to find the wattage, or the amount of power the appliance consumes. To find out the wattage, look for a serial platea rectangular strip of metal about 1 1/2 inches by 4 inches (3.5 cm by 11 cm) that's attached to the appliance, with a combination of amps, volts, and watts listed on it. (There also may be an EnergyGuide on larger appliances like refrigeratorssee Keywords). In some instances, a serial plate will not give wattage, but amperage and voltage instead. In this case, multiply the amperage by the voltage to get wattage. Note: In those cases where wattage isn't supplied, your best bet is to multiply amperage times voltage to get wattage, and most electrical companies will agree with that estimate. However, this method of determining watts from amps and volts, and from an alternating current, will only produce a rough estimate. Finding an exact measure of watts from amps and volts is a very complicated mannerit would take a week of electrical engineering lectures on alternalting current theory to explain, and that's probably more than you have time for now.
Multiply each item's wattage by the number of hours you've determined you use it per month. Take that result and divide it by 1,000this produces the number of kilowatthours that the item consumes each month. Write this figure down in the third column of the final report.
Almost doneone last easy calculation. Multiply item's monthly kilowatthours by the electric company's rate for a kilowatthour. The result is how much you pay to run the appliance each month. Write this figure down in the last figure of the final report. You've now done a careful estimation of the energy consumption and costs of a single electrical appliance.
