Amazon’s data center efficiency guru James Hamilton had a post Sunday night breaking down the recent report from Facebook, which detailed the company’s energy footprint and how much power is used by its data centers. Facebook’s total carbon footprint in 2011 was 285 metric tons of CO2 corresponding to 532 million kilowatt hours of electricity. At a very low electricity rate of 4 cents/kilowatt hour, Facebook would have dropped about $21 million on power last year.
What’s interesting about Hamilton’s post is that he uses the total power consumed rate by Facebook to figure out how many servers the company has. You can do this by starting with the average of power delivered to the IT infrastructure and dividing it by an estimate of the per server wattage (in this case Hamilton estimates 300 watts/server). Hamilton estimates that Facebook is now running at least a 150,000, and probably more like 180,000 servers, while he estimates that Google is running about a million, below even what forecasters had thought Google would have by now. The Google number is relatively low, pointing to the fact that Google has made strong efforts in efficiency and server utilitization which have allowed it to purchase relatively few servers. Second, Facebook’s server count is growing pretty fast, and will ultimately drive the company to further focus on the efficiency of each workload.