The Green Grid and a global taskforce created to harmonize metrics and measurement protocols for key energy efficiency metrics, have announced agreement on measurement guidelines and next steps for three new efficiency metrics. The taskforce reached consensus on the use of the Green Energy Coefficient (GEC), Energy Reuse Factor (ERF) and Carbon Usage Effectiveness (CUE) metrics. Details of their conclusions and recommendations for use of each metric are available in a memo titled, “Harmonizing Global Metrics for Data Center Energy Efficiency.”

In February 2011, the taskforce reached agreement on specific measurement protocols for the Power Usage Effectiveness (PUE) metric, developed by The Green Grid. Made up of the U.S. Department of Energy’s Advanced Manufacturing Office and Federal Energy Management Programs; the U.S. Environmental Protection Agency’s ENERGY STAR Program; the European Commission Joint Research Center Data Centers Code of Conduct, Japan’s Ministry of Economy, Trade and Industry; Japan’s Green IT Promotion Council; and The Green Grid, the taskforce intends to continue collaboration as an ongoing effort to improve data center energy and Greenhouse Gas (GHG) emission efficiencies.

The three new metrics were selected through discussion, exercise, and trial among the taskforce participants. The memo provides a framework for users to approach the metrics holistically, ensuring data center owners and operators can consistently assess and improve the performance of their mission critical facilities using energy efficiency metrics.

“We want to make it as easy as possible for the data center community to understand and embrace these metrics, and how they can work together,” said Joyce Dickerson, board member, The Green Grid. “When implemented correctly, they can save organizations a lot of time, money, and additional resources. Although there is more work to do, we think this will bring us one step closer to a universally adopted set of metrics, indices, and measurement protocols that will have a positive impact on the industry.”

The metrics and their purposes include:

• Green Energy Coefficient – GEC quantifies the portion of a facility’s energy that comes from green sources. The metric is computed as green energy consumed by the data center (kWh) divided by total energy consumed by the data center (kWh). 

 • Energy Reuse Factor – ERF identifies the portion of energy that is exported for reuse outside of the data center. ERF is computed as reuse energy divided by total energy consumed by the data center.

 • Carbon Usage Effectiveness – CUE enables an assessment of the total GHG emissions of a data center relative to its IT energy consumption. CUE is computed as the total carbon dioxide emission equivalents (CO2eq) from the energy consumption of the facility divided by the total IT energy consumption.

The memo and resulting agreements complete the second desired outcome of the taskforce and outline the two remaining deliverables for the group: Desired Outcome (1) Agree on effective energy efficiency metrics that measure actual IT work output of a data center compared to actual energy consumption and Desired Outcome (1.a) Measure the potential IT work output compared to expected energy consumption; and measure operational utilization of IT Equipment.  The group convenes regularly with representatives from each organization meeting in person every six to 12 months.

For more information about Harmonizing Global Metrics or to download the full memo, visit: