From what I've seen Google probably owns around 2-3% of the world's servers, which is probably on the order of 2 million machines.

Google claims that their datacenters use 1% of the estimated electricity consumption for data centers world wide and that their data centers are about twice as efficient as the average data center.

While those conclusions appear to be drawn from data that is several years old, it seems reasonable to assume that Google hasn't grown at a rate substantially different from the industry as a whole.

Maybe they own 4% of the world's servers, but very probably not 10% and certainly not 40%.