Move over, Power Usage Effectiveness (PUE). There’s a new energy-efficiency metric in town. Well, there’s actually three, but they’re not quite finished yet. The Green Grid, an international consortium of companies and individuals devoted to reducing power usage in data centers, announced late last week that it had reached agreement on measurement guidelines and next steps for three new efficiency metrics: Green Energy Coefficient, Energy Reuse Factor, and Carbon Usage Effectiveness. But that doesn’t mean PUE is going away anytime soon—according to Green Grid, it’ll remain the primary metric used to evaluate a data center’s energy efficiency, albeit in a more streamlined form. Specifically, Green Grid is assigning arbitrary efficiency values to better compare different implementations, including the purchase of chilled water for use within the data center’s cooling system. On top of that, data centers won’t receive PUE “bonus points” for reusing energy within the facility, or using waste heat to power or heat other facilities nearby. The new metrics are as follows:
  • GEC is a metric that quantifies the portion of a facility’s energy that comes from green sources. It is computed as the green energy consumed by the data center (kWh) divided by total energy consumed by the data center (kWh).  For the purposes of GEC, Green energy is defined as any form of renewable energy for which the data center owns the rights to the green energy certificate or renewable energy certificate, as defined by a local/regional authority.
  • ERF identifies the portion of energy that is exported for reuse outside of the data center. It is computed as reuse energy divided by total energy consumed by the data center.
  • CUE is a metric that enables an assessment of the total greenhouse gas emissions of data center, relative to its IT energy consumption. It is computed as the total carbon dioxide emission equivalents (CO2eq) from the energy consumption of the facility divided by the total IT energy consumption. For data centers powered solely by electricity, this is equivalent to multiplying the PUE by the data center’s carbon emission factor (CEF).
In formulating the new metrics, Green Grid joined forces with a global task force made up of the DOE, the EPA’s Energy Star Program, and European and Japanese agencies. “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,” Joyce Dickerson, a board member of the The Green Grid, wrote in a statement. “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.”   Image: Krivosheev Vitaly/