Reader comments pouring on for “iMac keeps its power promise”

Thanks, everybody, for the great comments to my post on iMac’s power efficiency. Keep it going, especially responses to my challenge to identify a Windows PC with comparable power efficiency. Machines built on Intel’s Viiv platform are leading the race, but it’s a new category.

Meanwhile, Chris wants to know about the nuts and bolts:

That seems almost fantastical – how did you measure the draw? I’m no electrical engineer, does it use a higher amperage then?

I stood outside and timed the revolutions of the little wheel in my electric meter.

I don’t have the attention span for that. Instead, I used a miraculous little box called the Kill A Watt from P3 International. It claims .2 percent accuracy and an engineer who tested it against some really scary bench equipment (link is PDF) proved the veracity of P3’s claims.

iMac’s power draw is not too fantastical once you consider that iMac is more or less a notebook with a super-bright display and no battery to charge. I feared that Apple’s engineers, given that iMac always runs on AC, might have traded power efficiency for accelerated time to market. They didn’t. Boucoup good on ’em.

As for Watts and Amps, I’m no EE either, but with voltage constant (120-121V here), the formula Watts = Volts x Amps means that as amperage (“current velocity” is my sloppy approximation) changes, Wattage (work accomplished) comes along.