Review: Kill-a-Watt electricity usage monitor

In June I shared some tips for reducing home energy costs. Most of the information came from Michael Bluejay's excellent guide to saving electricity. I was curious how much electricity invidual appliances use, so I ordered a gadget that Bluejay recommends: the Kill-a-Watt electricity meter. The official web site declares:

Connect your appliances into the Kill A Watt™, and assess how efficient they are. A large LCD display counts consumption by the Kilowatt-hour just like utility companies. You can figure out your electrical expenses by the hour, day, week, month, even an entire year. Monitor the quality of your power by displaying Voltage, Line Frequency, and Power Factor.

I've gone through our house and measured the power consumption of random devices:

  • Microwave (while dormant, simply displaying time): 2 watts — It costs us roughly $2/year to leave the microwave plugged in all the time.
  • Microwave (while heating a bowl of homemade bean soup for dinner): 2020 watts
  • Nintendo Wii (while playing Trauma Center: Second Opinion): 16 watts — Far less power than I would have guessed.
  • Strand of Christmas lights: 39 watts — More than I would have guessed. It will cost us roughly $3 to have this strand of lights plugged in during the Christmas season.
  • MacBook Pro (recharging with battery at 66%): 58 watts
  • Oil-filled radiator-style space heater: 520 watts on low, 820 watts on medium, and an unknown amount on high. I tripped the circuit breaker when I tried.
  • Dual-control electric blanket (one side set to three, the other turned off): 80 watts, declining by a watt every few seconds (presumably because it requires less power as it gets warmer — I don't know). I stopped watching after it had dropped to 58 watts.
  • Desk Lamp: 5 watts
  • Nighlight: 1 watt — Assuming the nightlight is on 12 hours/day, it costs about 50 cents to run for an entire year.

While researching this post, I learned that cable boxes are hidden power hogs. It hadn't occurred to me to test ours, but I'll do so tonight. (I read one report of a cable box drawing 100 watts. If you leave yours on 24/7 as we do, that's about $100 a year!)

The Kill-a-Watt's best feature is the ability to measure power consumption over time. If I want to see how much power the cable box really draws, for example, I can leave it plugged into the Kill-a-Watt. After a few days, I can check the cumulative power consumption in kilowatt hours and compare it to the amount of time that has elapsed. (Both of these are measured by the device.) Simple arithmetic will show me how much I'm spending to power the cable box!

The Kill-a-Watt does have some minor drawbacks:

  • The unit doesn't measure power consumption for large appliances like a range, or a washer or dryer.
  • The unit itself is rather bulky. When you plug it in, it's tall enough that it crowds (and usually blocks) the other receptacle in a standard outlet.
  • The screen can be difficult to read, especially for a chubby old geek like me. The readout is relatively dim, and most outlets are located near the floor. I had to do a lot of crouching and crawling to make readings.
  • The user must do some math in order to figure out overall power usage and, especially, how much the usage costs. Fortunately, the math is relatively simple.
  • Once you have the initial information, the Kill-a-Watt isn't very useful. It's not a tool you will use all the time.

I find the Kill-a-Watt fascinating. It makes an abstract topic concrete. I can read all sorts of tips about how to save energy, but they're all rather esoteric until I can actually see the numbers in front of me. The Kill-a-Watt gives me those numbers.

Note: I purchased this device using Amazon credit earned from this site. I also purchased several personal finance and self-development books for future review. I hope to begin “re-investing” some of the site revenue in items to review and to give away to readers.

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