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Data Center PUE: How Low Should You Go?

Date posted: June 5, 2012  Posted by

Go to any data center conference or sit in any data center planning meeting and you’re bound to hear a healthy discussion on PUE– power usage effectiveness. That’s hardly surprising given the business landscape of the last 20 years. Since the early 1990s, companies have been laser-focused on efficiencies, identifying and eliminating waste in any form that doesn’t add value, including time, materials, dollars and headcount.

In this business environment, reducing the ongoing costs of operating a data center is a no-brainer. That means the lower you can get your PUE the better, right? Hold on to that question for a moment.

PUE measures how efficiently a computer data center uses its power. It’s a simple ratio of total facility power (for computer equipment plus cooling, lighting, etc.) to computer equipment power. Every watt of power consumed by a data center over and above the energy required to run the computers increases the PUE. A PUE of 1.0 would mean the data center is not using any additional power beyond that needed for the IT equipment.

Think of PUE as the automotive equivalency of fuel efficiency. Every car owner wants good fuel efficiency. Who wouldn’t? But when it comes to buying a car, there are always other considerations: size, comfort, engine performance, handling, safety record, interior and exterior styling, entertainment package, storage, maintenance costs, resale value, and so on. The point is car owners rarely consider only fuel efficiency.

The same logic holds true for data centers.

Now back to that question: Is designing a data center to reach the lowest possible PUE always the best decision? We don’t think so. Our advice is to build a data center to meet your overall goals, keeping the big picture in mind.

Time and again we see owners willing to invest lots of time and money to achieve lower PUEs, and yet fail to analyze if it’s the right business decision. Building a data center is a business decision just like any other. What business would invest money without first looking at ROI? Keep in mind most data centers are still located in areas of the country where energy is inexpensive. Even modest PUE improvements add significant cost to your projects making payback periods very long or even non-existent.

Is PUE important? Absolutely. So is ROI. So are your other goals for the project. When you’re designing your next data center, make sure to consider all of these factors in the context of your overall goals.