When statistics attack

If you hadn’t already noticed Google has gone dark today. In honor of Earth Hour Google’s changed the background color of their home page from its usual white to black. Over on TechCrunch Michael Arrington has been scoffing at how ironic this is:

We criticized Google when we first posted about this because, it turns out, black web pages actually may use more power than white ones (based on a study that Google itself cited last year). So Google is, ironically, causing people who visit their site to use more power to celebrate Earth Hour than they would on a normal day.

The following is what the post that Arrington references by Bill Weihl on the Official Google Blog has to say:

…on flat-panel monitors (already estimated to be 75% of the market), displaying black may actually increase energy usage. Detailed results from a new study confirm this.

So there you have it. A black Google increases the power consumption for 75% of the market, therefore Google going black uses more energy than a white Google. Michael Arrington says so. Google says so. It must be so. Slight problem: There’s no way to draw that conclusion with that amount of information.

The critical missing pieces of information are: How much of an increase in power consumption does the black background cause on LCD monitors, and how much of a decrease in power consumption is realized with CRT monitors? The “new study” that Weihl mentions, by Darren Yates of Techlogg.com, comes the closest to providing that information.

Yates’s study, while not a rigorously scientific sampling, attributes an average power increase of 0.1 Watts across 23 LCD monitors to the change from white to black, but an average power savings of 10.8 Watts from the 4 CRT monitors tested. If we take these figures as reliable, this means it would take more than 100 LCD monitors to wipe out the energy savings of a single CRT with Google running a black background.

In other words, LCD monitor penetration would have to exceed 99% in the market before Google’s move would actually be wasting energy.

A little information is a dangerous thing.