Sunday, October 21, 2007

Energy Consumption of Various Appliances

Since electricity makes no sound, most people are in the dark about what is consuming electricity in the house at any particular time. Plug your computer, toaster, various power strips, TV and so forth into a Kill a Watt meter and you’ll undoubtedly find some unexpected energy drains. If you leave the appliance plugged into the Kill a Watt for a couple weeks, it will give you the total energy consumed in that time period, which will provide a good sense of how much the appliance uses per year.

Here’s what I learned by using it:


My thin-screen computer and All-in-1 printer use much more energy than the ones they replaced. In other words, as the need to reduce our carbon footprints becomes ever more pressing, many of us are unwittingly switching to the electronic equivalents of SUVs. (Note: newer laptops thankfully use much less energy, more like 20 watts.)
Dell PC (newer, with thin screen): 150 watts total
Dell PC (older, with big bloated screen): 35 watts total (50 watts when booting or with certain websites)
Mac Desktop (2003): 50 watts
Old HP printer: Zero watts when on but not in use
Newer All-in-One HP printer/scanner/fax/copier: 19 watts when on but not in use, 8 watts when turned off.
Old TV: 45 watts
New TV: Holding off on that one, but likely to be a big increase. A thin screen similar in size to our old 19" TV uses a similar amount of energy, so the new models are slim in looks only. (Note: As of 2011, a 40 inch LED thin screen TV uses about 80 watts. The LCD version used nearly twice that (I took a Kill a Watt meter to the store), and a plasma screen would use even more.)

It's called a dehumidifier, and it runs and runs. Mine is an Energy Star model, but that doesn't keep it from drawing what averages out to a constant draw of three or four hundred watts during the summer, and that's with it's thermostat set at the highest (70%) humidity level. A lower setting would cause it to run even more. Multiply that consumption rate by all the houses with basements, and you have a major contributor to energy demand, and therefore global warming. It may be worth looking into whether a ventilation system using fans that run on lower humidity days would achieve adequate results, simultaneously helping to reduce any risk of radon accumulation. Another measure is to make sure the ground slopes away from the house, and that downspouts discharge well away from the foundation, to reduce the amount of moisture seeping through the basement walls from the soil.

My refrigerator uses 170 watts when the motor is running. To my surprise, it can occasionally use far more when it is dead silent. Whenever the defroster kicks in, its energy consumption jumps to 630 watts. Not much to be done about that, except to minimize the time the door is open, and maybe check the settings to make sure it's not running colder than it needs to. One thing to look for inside the frig is the switch that "reduces exterior moisture". This is a heating element that's supposed to keep the door from sweating. I turned it off, didn't notice any sweating, and thereby avoided the constant draw of 7 watts. The light bulb in the frig also produces considerable heat when the door is open.

The DSL modem and router draw 9 watts combined. The TV/DVD/VCR draw 5 watts combined when not in use. Plugging these, along with printer and other computer peripherals into power strips that can be turned off reduces overnight consumption by about 30 watts. You can buy power strips that turn off peripherals automatically when the computer is turned off. I saw these on, but have yet to try them.

That's what they say about how comparatively expensive it is to heat anything with electricity. That little toaster oven on the kitchen counter, for instance, uses 1400 watts when on, nearly half of what the central air conditioner uses when it's cooling the whole house. Fortunately, toast is a quick operation. The hairdryer uses between 400 and 1500 watts, depending on the setting. The Kill-A-Watt wouldn't measure the electric clothes dryer's energy use, which turned out to be a mind-altering 3700 watts when measured with a whole house energy monitor called T.E.D. For comparison, a fluorescent light bulb uses 15 watts.

The Kill-a-Watt has its limitations. It would not measure the microwave oven, which apparently uses more electricity than the Kill-a-Watt is designed to handle. As it turns out, the microwave uses 1900 watts, not bad considering how quickly it heats things.

Vacuum cleaner: 1000
3-Way Lamp: 50-150 (quickly replaced with a one-way switch and a 23 watt flourescent)
Old stereo: 30-60, depending on volume