Measure and Optimize Your Household Power
By Kurt Johnson
Curious about the true energy use of your home and which appliances or devices draw the most power? Personal and cheap (about 15 bucks) electricity usage monitors like the Kill A WattTM allow you to measure the efficiency of appliances, electronics and lighting in your home – essentially auditing your electricity use. The device is able to measure Volts, Amps, and Watts, as well as the ability to measure over time via Kilowatt Hours (KWH). The Kill A Watt allows you to plug your appliance into the front of the device, then in turn plugs into a standard electrical socket. The device is able to monitor both standby power (aka “vampire power”) as well as active use. In addition to measuring energy efficiency, the included literature claims that the Kill A Watt is “perfect for detecting voltage drops and brownout conditions before they damage delicate equipment…the knowledge you gain…can save you thousands of dollars” – presumably by ensuring consistent power to your electronics.
I’m no electrician or mathematician, so I opted for the simplest method of measurement, measuring current-use wattage levels for each appliance, some in standby mode as well as those actively drawing power. Note that measuring by the KWH (measuring power use over a time period) is likely the best method of measurement.
The results of my simplistic test were interesting and eye-opening in terms of what draws the most power in my house, as well as comparative use between appliances. Some appliances were immeasurable with the device, like the 220 Volt oven and dryer. I also opted out of measuring the refrigerator, since moving it out from its alcove is a monumental task and probably would have damaged both my back and the linoleum in my kitchen. The refrigerator is a massive power draw, however, and should be measured to assess power use if you plan on doing so. A typical family refrigerator draws between 400 and 800 Watts. Mine is fairly new and efficient, so I chose 500 Watts as a middle-ground estimate.
The most efficient actively-powered standard appliances in our home included the land-line phone at 1.2 Watts, the mini-stereo at 8.6 Watts, and a compact fluorescent lightbulb (CFL) lamp at 15.7 Watts. Devices that drew the most “vampire power” included personal computer accessories and peripherals that are always on in standby mode. Without the computer being “on”, the monitor, speakers, modem, wireless modem, and printer accounted for 35.2 Watts. With the power strip switched to “off”, 35.2 Watts dropped to zero.
Big power users in my home included the water heater (estimated 2,400 Watts when running), my refrigerator (estimated 500 Watts) and the computer and accessories when fully powered at 250 Watts. The greatest power draw I measured with the Kill A Watt was the microwave when running, which drew 1735 Watts. Common household big energy consumers include ovens and ranges (12,200 Watts!), swimming pool pumps (2,000 Watts), clothes dryers (2,790 Watts), dishwashers (1,201 Watts), and hair dryers (1,000 Watts).
It was interesting to compare the power use of a CFL lamp (15.7 Watts) to my Comcast cable box, which drew nearly twice the power (25.3 Watts). My Roomba robot vacuum cleaner recharger constantly draws 7.2 Watts, which is half the power use of the CFL lamp when on! And it was helpful to be aware of energy efficiency at the individual appliance level, serving as a reminder to conserve energy, turn off power strips to eliminate “vampire power”, and maintain my appliances for best performance (e.g. cleaning the coils on my refrigerator or cleaning the dryer vent). By measuring your devices and being aware of their power use, you too can better understand and manage energy.
The following is a table of measurements and estimates, illustrated by a power use pie chart.
|Lamp (with CFL)||15.7|
|Roomba Vacuum Cleaner charger||7.2|
|TV and Accessories (Off)||22|
|TV and Accessories (On)||71.6|