Energy cost is the fastest growing expense for many data center managers. There has been significant progress in the industry to identify measurements that would track the the efficiency of energy usage.
The Green Grid
“The Green Grid is a global consortium of IT companies and professionals seeking to improve energy efficiency in data centers and business computing ecosystems around the globe. The organization seeks to unite global industry efforts to standardize on a common set of metrics, processes, methods and new technologies to further its common goals.”
The two most commonly used metrics today, originally developed and popularized by The Green Grid consortium, are Power Usage Effectiveness (PUE) and its reciprocal, Data Center Infrastructure Efficiency (DCiE). Using these metrics data center executives can quickly determine if their energy performance is efficient relative to a common measuring system. A third metric, Carbon Usage Effectiveness (CUE) has also recently been introduced by The Green Grid consortium.
For more detailed information on PUE and DCiE, you can review a white paper published by The Green Grid at the following: White Paper on PUE and DCiE.
Power Usage Effectiveness (PUE)
PUE is intended to identify the efficiency of power use in comparison to the desirable use of power – powering computer equipment. In essence, PUE is an overhead ratio. The ideal goal is to achieve a PUE of 1.0 — where all power usage would be for computing equipment. The overhead uses for power would include lighting, power back-up, and the largest non-computing use of power, data center cooling. While the current industry average is approximately 2.1, the objective is to be as close to 1.0 as possible. The formula for calculating PUE along with an example is listed below:
- PUE = (Total facility power) / (IT equipment power)
- PUE = 200 kW / 110 kW
- PUE = 1.81
Data Center Infrastructure Efficiency (DCiE)
DCiE is intended to express power usage efficiency as a percentage, similar to a traditional report card. The ideal goal is to achieve 100% of power usage is for computing equipment directly. The closer DCiE is to 100%, the more efficient the data center in terms of power usage. The formula for calculating DCiE along with an example is listed below:
- DCiE = (IT equipment power) / (Total facility power) x 100
- DCiE = 110 kW / 200 kW x 100
- DCiE = 55%