Whose data centers are more efficient? Facebook’s or Google’s?

Google is a total champ when it comes to its infrastructure, and a blog post Monday shows the search giant is running its data centers at a power usage effective (PUE) of 1.14. The PUE metric is a measure of how much extra power is required to provide each unit of compute. So, in Google’s case, its data centers only use 14 percent more power for everything that isn’t the servers.

But wait, is that right? Google later in the post claims that the version of PUE that gives it the 1.14 ranking is more comprehensive than others tends to use. Google tosses in power lost to AC/DC conversions, cooling offices associated with the data center and other bits and pieces. Counting only the servers and the air conditioning gives Google a PUE of 1.06. So why might this matter? Well, PUE is the metric to beat in the race to greener data centers, and Google may have just beat Facebook’s Prineville data center by a tenth of a percent.

From the blog post:

To calculate this number we include everything that contributes to energy consumption in our data centers. That means that in addition to the electricity used to power the servers and cooling systems, we incorporate the oil and natural gas that heat our offices. We also account for system inefficiencies like transformer, cable and UPS losses and generator parasitic energy draw.

If we chose to use a simpler calculation-for instance, if we included only the data center and the cooling equipment—we could report a PUE as low as 1.06 at our most efficient location. But we want to be as comprehensive as possible in our measurements. You can see the difference in this graphic:

The average data center PUE is about 1.8, but Facebook, with its Open Compute-designed servers and focus on designing everything from the data center all the way to the application, has a PUE of 1.07. But we’re still waiting for Facebook to say whether or not its PUE measurements include the everything-but-the-kitchen-sink metric Google is using, or the more-simplified version.

Either way, Google and Facebook are some of the few firms getting close to the ideal PUE of 1. Meanwhile, other data centers are seeing how low they can go. Recently, eBay announced a new data center that has a PUE of 1.35, and Yahoo has designs that can deliver a PUE of 1.08.

However, some of the largest data center owners in the world, including Amazon, Microsoft and Apple, so far have refrained from making their PUEs public. Microsoft said last year that it would aim for a PUE of 1.25 across all of its data centers by April 2013. Amazon’s data center guru James Hamilton published a presentation on Amazon last year that assumed a PUE of 1.45 for the online retailer’s data centers. Apple doesn’t appear to have said anything so far, although it has hired the gentleman behind Yahoo’s chicken coop design, with a PUE of 1.08, to manage its data center build out.

I’ve reached out to Apple, Amazon and Microsoft for more information on their current PUE status and will update the story if I hear back.

So, if the question is how low can you go, then Google and Facebook have more to crow about among the biggest operators, while Microsoft is improving, Amazon is a mystery and Apple is even more of a mystery. That sounds about right.

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