Is PUE really going up?

One of the more intriguing results of the Uptime Institute Global Data Center Survey 2019 concerned energy efficiency. For years, data centers have become ever more efficient, with power usage effectiveness (PUE) ratings across the industry (apparently) falling. Big operators, such as hyperscale cloud companies and big colos, regularly claim annual or design PUE figures between 1.1 and 1.4. It is an industry success story — a response to both higher power prices and concerns about carbon dioxide emissions.

Uptime Institute has tracked industry average PUE numbers, at intervals, over 12 years (see Figure 1). And this year, for the first time, there was no recorded improvement. In fact, energy efficiency deteriorated slightly, from an average PUE of 1.58 in 2018 to 1.67 in 2019 (lower is better). Can this really be right, and if so, how do we explain it?