I’ve always imagined getting an itemized electric bill. We’re not there yet, but when I saw a Kill-A-Watt at Radio Shack last night I remembered the discussion thread at this 2007 blog post and impulsively bought it.

In a way I’m glad I waited until 2009 because a companion tool is available now that wasn’t then: WolframAlpha. Its fluency with units, conversions, and comparisons is really helpful if, like me, you can’t do that stuff quickly and easily in your head.

So, for example, I’m sitting at my desk with the Kill-A-Watt watching my main power strip. I have a mixer here that I use about an hour a week for podcast recording. There’s no power switch because, well, why bother, just leave it on, it’s a tiny draw. Negligible.

I reach over and unplug it. Now I’m drawing 9 fewer watts. But what does that mean? I consult Wolfram Alpha:

Q: 9 W

A: About half the power expended by the human brain.

On a monthly basis?

Q: 9 W * (30 * 24 hours)

A: About half the energy released by combustion of one kilogram of gasoline.

In gallons?

Q: ( 1 kilogram / density of gasoline ) / 2

A: Less than a fifth of a gallon.

Relative to my electric usage, which was 1291 kWh last month?

Q: 9 W / (1291kwh / ( 30 * 24 hours)) * 100

A: Half a percent.

In dollars?

Q: 9 W / (1291kwh / ( 30 * 24 hours)) * $205.60

A: One dollar.

I find these comparisons really helpful. A dollar a month is a rounding error. But if I think of it as the energy equivalent of driving my car 7.2 miles, that makes me want to reach over and unplug the mixer for the 715 hours per month I’m not using it.

Saul Griffith has internalized these calculations, but most of us need help. A next-gen Kill-A-Watt that did these sorts of conversions and comparisons could be a real behavior changer.