Standards and Metrics

Power Usage Effectiveness (PUE)


Power Usage Effectiveness – PUE is the ratio of total amount of energy used by a data center facility to the energy delivered to computing equipment.  PUE was originally developed by a consortium called The Green Grid.

PUE was published in 2016 as a global standard under ISO/IEC 30134-2:2016

PUE rating becomes more powerful and useful when consistently calculated over time. PUE ratings can fluctuate during the work day/peak load compared to evenings and weekends. The Green Grid has produced the following frequency guideline for efficiency measurements:

▪️ Basic Efficiency Program: measured weekly/monthly

▪️ Intermediate Efficiency Program: measured daily

▪️ Advanced Efficiency Program: measured continually

Measuring PUE on a regular basis allows for a baseline and provides an accurate picture of how and where energy is being consumed.  It is extremely difficult to improve energy efficiency without this baseline. After the initial measurement is complete a remediation plan can be accurately developed and implemented. Regardless of the frequency of measurement, basic, intermediate, or advanced, consistency is the key and will significantly increase the probability of improving energy efficiency.

American Society of Heating Refrigeration & Air Conditioning Engineers (ASHRAE)

ASHRAE issued its first thermal guidelines for data centers in 2004 [1]. The original ASHRAE air temperature recommended envelope for data centers was 20-25°C(68-77°F). This was a conservative statement, based on data available at the time, on where a data center could be reliably operated. Reliability and uptime were the primary concerns and energy costs were secondary. Since then, ASHRAE has issued a recommended range of 18-27°C(64-81°F) and, in 2011, published classes that allow a temperature range of 5 to 45°C (41 to 113°F). The A3 (40°C, 104°F) and A4 (45°C, 113°F) classes were created to support new energy saving technologies such as economization.