The data center industry is still a long way short of a meaningful standard for energy efficiency, admitted David Snelling, Fujitu Labs representative for The Green Grid, speaking Tuesday at the annual DatacenterDynamics conference in London.

Snelling was hosting a private breakout session on global harmonization of metrics to gauge reaction to cross industry efforts to quantify data center energy efficiency. "We can only understand those values that we can measure," he said.

Of the metrics used to quantify efficiency, PUE has emerged as the best measure out of an imperfect basket of metrics, which also included ITEE, ITEU and GEC. "PUE is the most advanced metric but it still has a long way to go," he admitted. "The next stage of maturity would be standardization, after which we could anticipate a period of some kind of compliancy testing," he promised.

One impatient IT director from the London offices of a global investment bank voiced his impatience with the advance of standards. He outlined his organization's own compliance system. "PUE means nothing unless it's constantly measured," he said. In his bank's data centers the power and temperature are measured at rack level, constantly, he said. "We monitor the PUE and publish the figures on two big clocks every 30 seconds. If the PUE rises, the engineers act on it immediately. They're incentivized by bonuses to keep the PUE down," he said.

Electricity bills are the only accurate measure, said the banking IT manager. "If the PUE comes down we make our money back on the engineer's bonus by saving power."

Some members of the roundtable registered their dissatisfaction with energy consumption numbers IT vendors label their products with. "The nameplate figures are not relevant," complained an IT manager, "they quote values for a rack with a full complement of disks and memory, which nobody ever has."