It also seems to me a vast exageration, yet there are many hidden costs.

• google replies in a few seconds, but there are huge costs in crawling the net and precomputing the page ranks, which happen before your search (and you can't put a price tag on these for an individual search, because they are mutualized over all searches)

• the index and the link matrix for the page rank have to be stored on armies of hard-drives, which suck a lot of power even when there is no search, with present hard-drive technology.

• the computer of the end-user is in many cases a 500W monster, and not 40-60W like the iMac.

• you must count the power in all the DSLAM and backbone routers to carry the data (not only for the search, but also for the crawl, and crawlbots are now something like 10% of IP bandwidth - of course, they still pale in comparison to spam and porn fileswapping which together make up well over 50%)

I can still tell it's an exageration because google has something like 30 huge datacenters worldwide, so we are talking of much less than 1 million processing nodes, and there are much more running PCs anytime in the world (and they still make up for a small portion of total power consumption). Besides, google could be siting data centers in country with cheap/carbon-free electricity in the future (France, Iceland, under PVs in Nevada...)

Pierre