Green IT not-for-profit The Green Grid wants water used for cooling in data centres added to the metric for data centre power efficiency to adequately account for how much energy is actually used.
The group published a proposal for a revised PUE (power usage effectiveness) metric, the widely-used measure for a data centre's effiiciency.
It argued today's PUE doesn't account for the electricity and generator fuel for evaporative water cooling systems, and therefore fails to provide a true picture of data centre energy efficiency.
The group's proposed formular for a new PUE - PUER, or 'power usage effectiveness revised - takestakes into account site electrical energy (SEE), stand-by generator energy (SGE) and water equivalent energy (WEE) and IT equipment energy.
It said if the new formular was used, many of today's data centres with PUE close to the ideal 1.0 factor would actually be rated as having lower efficiency.
Green Grid member Emerson Network Power applied the new formula to a 1 mega Watt model data centre with a reported PUE of 1.10, and came up with a PUER of 1.42, a substantial disparity in performance.
The company said using the PUER formula would provide a meaningful analysis of different cooling options for data centres - those cooled with evaporation will have far higher PUER ratings than the current reported PUE metrics when water usage is taken into account.
Similarly, the National Australian Built Environment Rating System - NABERS - does not currently factor in water use for cooling in its energy efficiency ratings system for data centres.