Data center industry group The Green Grid has revised its guidelines for calculating its data center energy efficiency metric Power Usage Effectiveness (PUE) for the last time.

The new version of the guidelines completes the guidelines for applying PUE, the organization said in a statement.

The Green Grid said, alignment of the methodologies it proposed across the industry would "lead to consistent and repeatable measurement strategies" for monitoring and improving energy efficiency in existing data centers and those being planned.

The key piece in the new report is the specification of where total power for a data center in a mixed-use facility should be measured for the PUE calculation. The Green Grid says it should be all energy required to operate the data center, similar to a dedicated data center, and should include cooling, lighting, and support infrastructure for the data center operations."

The organization recommends that the total-energy figure excludes energy used by spaces the data center shares with other use types. These are spaces like offices, lobby or restrooms that are not used exclusively for the data center.

The Green Grid added a 0.03 condenser-water factor to the list of weighting factors for PUE calculations. This means an operator whose facility uses a condenser-water system, they should multiply energy used by their cooling system by 0.03 before calculating total energy.

The weighting factors for a variety of energy types ÔÇô including natural gas, fuel oil, district chilled water or steam, among others ÔÇô are used to account for all source of energy in data centers that use energy other than electricity from their utility.

Symantec's Dan Azevedo, one of The Green Grid's board members, said in a statement, the organization was looking forward to its next steps, which included other efficiency programs, such as IT productivity and carbon reporting.

"The task force has accomplished a tremendous amount of work to help the data center industry have a common understanding of energy efficiency metrics to improve data center efficiencies and reduce energy use," Azevedo said.