What Is Data Center PUE?

PUE And How To Calculate Data Center Efficiency

Operating costs for data centers are rising as users demand for more power rises and heat generation becomes an issue for operators. Many data centers strive to lower their costs in order to extend savings to customers. PUE, or Power Usage Effectiveness, is becoming a key tool used in selecting a data center for many clients.

The Green Grid TM has developed a standard to calculate how much power is being used by servers, storage equipment, telco equipment, network equipment, KVM switches and other components (IT Equipment Power or IEP) used in a data center in relationship to the power used to cool and run the data center. The total power used by the data center is called the Total Facility Power or TFP. The relationship between these two components is called the Power Usage Effectiveness or PUE. As the power usage from colocation clients changes within a data center, so can the PUE.

How Data Centers Calculate PUE

It is rather simple. The formula to determine PUE is simply divide the data centers Total Facility Power by the IT Equipment Power or


A PUE score of 2.5 indicates that the data center demand is two and one half times greater than the energy necessary to power the IT equipment.

  1. First you need to take the TFP, which is measured at the utility meter entering the data center. This measurement includes all the internal components like CRAC units, chillers, UPS, PDUs, security features, lighting and monitoring equipment required to provide service to the IT equipment load.
  2. Then measure the IT equipment load. This measurement is determined after all switching and conditioning is performed. The most reliable way to do this is at the power distribution units which should be the total power sent to the racks in the colocation facility.
  3. Dividing the two numbers TFP/IEP is the PUE. This determines how efficient the data center is running. The lower the number is towards 1 the better the efficiency is of the data center.

The average data center has a PUE of 2.0 to 2.5. Based on this calculation, one can assume that if a data center has a PUE of 2.0 that for every watt used of IT power, the data center uses an additional watt to cool the site and send power to the IT equipment. PUEs generally range from 1.4 to 3.

How Important Is the PUE?

The PUE is extremely important as power demands change within a data center. Caution must be taking by relying on the PUE quoted by a data center. If this number is extremely important in your decision, you should have a third party verify the numbers using actual utility bills. One needs to be somewhat suspicious of PUEs quoted since they can be measured at a most efficient moment in time and appear to be more efficient than the data center is over a period of time. Some critics point out that PUEs should be measure over a period of time to be real accurate.

Location of a data center can have a major impact on the PUE number as well. Climate benefits can impact the PUE. If a location can utilize free cooling methodologies compared to areas that have a high external heat environment, like San Diego or Phoenix, this can impact PUEs also. Make sure the PUE you are given was not taken during a period of free cooling.

About DataCenterAndColocation: www.DataCenterAndColocation.com Our data center consulting company, located in San Diego California, represents approximately 3000 data centers and colocation centers across the US. At no cost to our clients, we identify specific space, power and security requirements, solicit proposals, professionally analyze them, compare the strengths and weaknesses, negotiate pricing and deliver highly competitive bids for colocation. Whether you are moving your existing colocation site, adding data center sites or establish a disaster recover site, our service is your best solution to reduce costs and free employee valuable time. Our specialty is identifying very high quality and low power cost data centers.