Power Usage Effectiveness (PUE)

Power Usage Effectiveness (PUE) is a standard developed by The Green Grid‚Ñ¢ consortium to provide a clear answer to the primary issue surrounding energy efficiency within the data center which is how much power is devoted to driving the actual computing/IT components (servers, for example) versus the ancillary support elements such as cooling and lighting. With the rise of computing demands and high density computational environments, the power distribution expressed by either metric is extremely important. The components of the PUE calculation look at the relationship between “Total Facility Power” (TFP) and “IT Equipment Power” (IEP). TFP is measured at the utility meter for the data center space and includes all of the components required to support the IT load including:

  • Power components including UPS systems and PDUs
  • Cooling elements such as CRACs and chillers
  • Other infrastructure components such as lighting

As might be expected, IEP, or more simply, IT Load, is the sum total of the power used by the facility‚ computing components including servers, storage devices and networking equipment. The main difference between these two standards is the placement of each of these elements in their equations and their resulting output.

Calculating PUE

To calculate a facility‚ PUE simply divide the Total Facility Power by its IT Equipment Power. Your answer will be a whole number. For example, a PUE score of 3 indicates that the data center demand is three times greater than the energy necessary to power the IT equipment.

Interpreting PUE

The PUE can range from 1 to infinity. In the case of the PUE, data center energy efficiency increases the closer the number comes to one which indicates that a greater portion of the power required by the facility is used to drive the IT equipment.