October is Energy Awareness Month, a good time to think about how you are using energy and how you can use less of it. Using less energy will reduce greenhouse gas emissions and will protect the environment. And of course, using less energy will lower your monthly electric bill.
To better understand how much it costs to operate a particular appliance per month, here is a simple formula you can follow.
Step 1. Determine the appliance’s wattage and convert it to kilowatts.*
_____ watts / 1000 = _____ kilowatts
Step 2. Enter the average number of hours you use the appliance per month.**
_____ hours
Step 3. For the cost per kilowatt, assume 23¢ per kilowatt-hour (kWh), the effective rate on Oahu for September 2009. See below for other rates.*** (The rate fluctuates monthly due to the change in the cost of fuel.)
Step 4. Calculate the operating cost by multiplying the results of steps 1, 2, and 3.
_____ kilowatts x _____ hours x $0.23 per kilowatt-hour = cost to operate the appliance
Example: 145-watt 24-inch Sony Trinitron TV
0.145 kilowatts x 120 hours x 0.23 per kilowatt-hour = $4.00 per month
* The wattage of an electric appliance is usually listed on a metal plate on the back or bottom of the appliance. If only the amps and volts are listed, multiply the amps times the volts to get watts.
* Electric motors are often rated in horsepower. One horsepower is roughly equal to one kilowatt.
** Some appliances, such as refrigerators, water heaters, air conditioners, dryers, electric skillets, irons, and ovens, are controlled by thermostats that cycle on and off automatically. This type of appliance uses energy only when the heating element or motor is on. To figure its energy use you need to estimate the amount of time it is operating at full load.
***For Kauai, Lanai, and Hawaii use 32 cents per kWh. For Molokai use 30 cents per kWh. For Maui use 25 cents per kWh.
