You can often determine the amount of wattage an appliance uses simply by reading the label on the appliance, but if you don't know how that wattage converts into kilowatts, it makes it hard to determine if your appliance is energy-efficient. Your electricity is billed in kilowatt hours, so figuring out how much your appliance costs to operate takes a few calculations. Once you learn how to determine the amount of kilowatts an appliance uses, you can make better choices when purchasing new energy-efficient appliances.
Look on your appliance for the Underwriter’s Laboratory (UL) label. This label normally lists the name of the appliance, the model number and the manufacturer. Some labels list the amperage, voltage and wattage of the appliance, while others may list only the voltage and the amperage. If your label does not list the wattage, but lists the volts and amps, you must calculate the wattage of the appliance before determining kilowatt usage.
Find the amperage listed on the UL label. Multiply that by the voltage of the appliance. For example, the UL label on a refrigerator shows the appliance uses 115 volts and draws 6 amps. Six amps multiplied by 115 volts equals 690 watts.
Divide the wattage of the appliance by 1,000 to determine the kilowatts used by the appliance. Divide the refrigerator’s 690 watts by 1,000 to determine the refrigerator uses .69 kilowatts.
Multiply the wattage of the appliance by the number of hours a day you use that appliance. Multiply that number by the number of days you use the appliance in a year. Divide the total by 1,000 to determine how many kilowatts that appliance uses per year. You can also multiply the kilowatts used per year by your kilowatt hour cost from your electric company to determine how much that appliance costs to operate a year.
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