We pay for electricity in kilowatt-hours (kwhs). One kilowatt-hour is the equivalent of using 1,000 watts for one hour or using a 100-watt light bulb for 10 hours. When kilowatt-hours add up, electric bills get higher. And kilowatt-hour usage is adding up more and more each year. According to statistics, the average family's use of electricity is increasing at a rate of 4 to 7 percent each year.
To calculate the exact use of your appliances, use the following formula. (Look for the serial plate on the bottom or back of the appliance. It lists the power used in terms of watts (w) or amps and volts.)
• amps x volts = watts
• watts x hours = watt-hours
• watt-hours / 1000 = kilowatt-hours (kwhs)
• kwhs x Residential Electric Rate* = estimated cost of using appliance
EXAMPLE: We will use an electric hand mixer as an example. This appliance requires about 127 watts. Following is how you would figure its usage for 15 minutes:
• 15 minutes = 1/4 hour, so 120 watts x 1/4 hour = 30 watt-hours
• 30 watt-hours / 1000 = .03 kwhs
• .03 kwhs x .065 cents = .19 cent (nearly two-tenths of one cent)
For a larger appliance such as a water heater, remember that it is only running when it has clicked on and is heating water. The time your water heater is on varies according to how often you do laundry, take baths or run the dishwasher. For this example, let's assume your water heater is on for three hours on a particular day (the national average).
• 4,500 watts x 3 hours = 13,500 watt-hours
• 13,500 watt-hours / 1000 = 13.5 kwh
• 13.5 kwh x .065 cents = 87.8 cents
Or, from another angle, you can see that you would use 4.5 kwh for every full hour that your water heater is on. That means it costs you 29.2 cents per hour.