How to Calculate Appliance Energy Use

QUESTION:

How can I calculate the cost of energy used by my electric appliances?

ANSWER:

For "simple" appliances—like light bulbs, irons, hair dryers, TVs and radios—you can multiply the device's wattage rating* by the number of hours you use it each month. Divide your answer by 1000. That tells you how many kilowatt-hours (kWh) of electricity the appliance uses per month. Finally, multiply the kWh by your electric cost (which, on an annual basis, currently averages about 9.5¢ for the majority of CWLP's residential customers).

This calculation method doesn't work well for more complex systems—especially air conditioners, refrigerators, water heaters, and other appliances that cycle on and off during operation. For help estimating the energy use of these types of appliances, you can contact the Energy Services Office.

More information about calculating appliance energy usage, including a chart listing the approximate energy use of many common household appliances, can be found on our Appliance Energy Use page.

* NOTE: If you do not know how many watts your appliance uses, you can calculate it if you know the appliance's amperage and voltage. Most household appliances operate on 110 volts; a few, such as electric clothes dryers and stoves/ovens, require 240 volts.

Wattage = amps x volts.