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Everything you Need to Know About PUE

10 November, 2015

Power Meter

It’s all well and good trying to implement energy efficient changes and installing the most eco-friendly equipment, but it could all be in vain if there is no way to measure its effectiveness. That’s why it was proposed that there needed to be a widely accepted way to determine how energy efficient data centres are, and also a way to monitor improvements and have a standard to aim for.

PUE (Power Usage Effectiveness) is how energy efficiency is measured in data centres around the world. It enables organisations to understand the level of power consumption and efficiency in a facility, and allows them to gauge the effectiveness of energy reduction efforts.

PUE Facts

  • The PUE metric was introduced in 2006 by the Green Grid
  • It is calculated as a ratio
  • It’s the most popular way of measuring energy efficiency
  • The ideal PUE which companies should strive for is 1.0, but they generally range from 1.4 to 3
  • Date centres with a low PUE have low running costs and vice versa

How to Calculate PUE

To figure out the PUE of a data centre, you just need to divide two figures: the Total Facility Energy and the IT Equipment Energy.


PUE represents how much power used by a data centre is used up by the IT equipment, in contrast to the power used by lighting, cooling and other operations within the facility.

Step 1 – Take the TFE measurement, which is usually measured at the utility meter entering the data centre. This figure should include all applications which service the IT equipment, such as chillers, lighting and monitoring equipment.

Step 2 – Take the IT equipment load, which should be measured after switching and conditioning is performed.

Step 3 – Divide the two numbers, TFE by ITEE.

A PUE score of 2.0 means that for every watt of power used by the IT equipment, another watt is needed to send power to the equipment and to cool the data centre.

The average data centre has a PUE of 2.0 – 2.5, but the lower the better. It’s a good idea to calculate your PUE regularly to take note of any changes n energy efficiencies, and to figure out the best strategies for improvement.

Refer to The Green Grid’s White Paper on the PUE metric for further information about measuring and improving PUE.


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