Saturday, April 21, 2012

Unplugging small appliances

There is time for one more post before Earth Day tomorrow. This week I have told you about freezer and refrigerator temperatures, hot water temperature, and energy-efficient lighting. Let's talk about one more way to save electricity.

Most electric appliances consume energy as soon are they are plugged in, whether they are actively used or not. The power is drawn from digital clocks and displays, remote controls, or voltage regulators, and can be as high as 10 to 15 watts. This standby power is sometimes called "phantom load."

How to measure your energy usage
You can use a wattmeter to measure the electric power of any device plugged to an outlet. (Some public libraries lend wattmeters.)
  1. Plug the wattmeter to the electric outlet.
  2. Plug the device to the wattmeter.
  3. Read the power usage in watts when the device is running.
  4. Read the power usage in watts when the device is in standby mode (that is, plugged in but not performing its main function).
You can then compute the yearly energy usage of your appliance with the Energy Usage Calculator provided below.

When the appliance is in use, the wattmeter indicates how much power is needed to run the appliance. This allows you to compute how much energy you consume by using your appliance and encourages you to think of a less powerful appliance to use or to use it for shorter periods of time.

When the appliance is in standby mode, the wattmeter indicates its phantom load. This allows you to compute how much energy is wasted by keeping your appliance plugged in when not in use.

Energy Usage Calculator
Daily Appliance Usage:
Measured Power (in Use):
Measured Power (Standby):
Electricity Rate:
Yearly Energy Usage:
Yearly Energy Waste:
Percentage of Energy Wasted:
(Numbers are shown as an example. Enter your own data.)

When your coffee maker is in use, the wattmeter reads 800 watts. The coffee maker is in use for 30 minutes (or 0.5 hours) every day. Your yearly energy usage is 145.6 kWh/year. At a rate of $0.12233 per kWh, brewing coffee costs $17.81 per year.

When your coffee maker is in standby mode, that is, when you aren't brewing any coffee but the digital display is on, the wattmeter reads 3 watts. If the coffee maker is plugged in around the clock but you actively use it for only 30 minutes every day (that is, it is in standby mode 23.5 hours per day), the energy wasted in a year is: 25.7 kWh/year, which translates into $3.14 per year.

In this example, 15 percent of the energy consumed by the appliance is due to phantom load, and is thus wasted.

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