About PUE
Energy efficiency is rapidly becoming a key data center issue. The more energy efficient the data center, the lower the on-going operating costs which obviously increases any business’ bottom line.
What is PUE?
Power Usage Effectiveness (PUE) is a standard developed by The Green Grid™ consortium to provide a clear answer to the primary issue surrounding energy efficiency within any data center. It considers how much power is devoted to driving the actual computing/IT components, like servers, 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.
These measurements include:
- 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’s 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 respective output.
Calculating PUE
To calculate a facility’s PUE simply divide the total facility power by its IT equipment power. A PUE score of 3 indicates that the data center demand is three times greater than the energy necessary to power the IT equipment. Which would categorize the data center as “very inefficient” (see chart below).
Interpreting PUE
A PUE score is no lower than 1 and can be any infinite positive number. In the case of the PUE, data center energy efficiency increases the closer the number comes to 1, which indicates that a greater portion of the power required by the facility is used to drive the IT equipment.