Power Assure rating
There are several metrics for evaluating data center efficiency, such as Power Usage Effectiveness( PUE), Carbon Usage Effectiveness ( CUE), Hardware Utilization Efficiency (HUE), Water Usage Effectiveness(WUE), and Corporate Average Data Center Efficiency ( CADE).
Because the various PUE metrics favor inefficient servers that require more energy for cooling, Power Assure created PAR4, a rating designed to address the drawbacks of the various ratings.
While the aforementioned metrics are based on power consumption, water consumption for cooling, or data center carbon dioxide emissions relative to energy consumption, PAR4 is based on the energy consumed while operating the data center and relates to computing power.
The PAR4 metric is thus similar to SPECpower, which relates server performance in operation to power consumed. In PAR4, servers are color classified from green to black. Green corresponds to the best rating and black to the worst. The classification is based on a point system. The better the PAR4 rating, the more interesting the products are, at least in terms of energy efficiency.