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What is Power Usage Effectiveness (PUE)?

Power Usage Effectiveness (PUE) is a calculation used to measure data centre energy efficiency. It was first introduced in 2007 and endorsed by The Green Grid to promote more effective data centre energy management. Nowadays, PUE is a global standard that companies use to assess and improve their energy consumption.

To calculate PUE, a company must determine two factors:

  1. Their IT load. This is the energy consumed by IT equipment and is typically measured from power distribution units (PDUs).
  2. Total facility energy consumption, including any network equipment, cooling systems, lighting, and uninterruptible power supplies. It’s usually measured from the utility meter.

PUE is an excellent tool for benchmarking data centre energy use over time, allowing companies to see the results of their changes and improvements.

 

PUE and Data Centre Energy Usage

Modern data centres host the critical IT infrastructure that many industries demand. While this IT equipment uses energy, it also generates a lot of heat. As data centres grow and provide more and more processing power, they must also keep their equipment in top condition through effective heat management, cooling, and use of space.

Data centre management can then use PUE to monitor their energy usage. Put simply, if a data centre has a high PUE ratio, it should explore areas to optimise energy consumption. Not only does lowering PUE reduce unnecessary energy spending, but it also contributes to energy saving initiatives, reducing emissions, and providing the best possible customer experience.

 

What is DCiE?

Data Centre Infrastructure Efficiency (DCiE) is another method of judging a data centre’s energy usage. It uses the same metrics as PUE but communicates results differently. While PUE is a ratio, DCiE shows the IT load as a percentage of total facility power usage.

How much energy does a data centre use?

Data centres use a lot of energy. This places a responsibility on  data centre providers to use less energy where possible. The widespread adoption of real-time business processes, machine learning, and high-speed connectivity means existing energy consumption could increase in the future.

So, with data centres accounting for 1 per cent of the world’s energy consumption, it’s critical to make improvements wherever possible. Both PUE and DCiE are vital tools in tackling unnecessary energy consumption.

 

How to calculate PUE and DCiE

The power usage effectiveness calculation is:

Total amount of Energy used / IT equipment energy usage = PUE data centre ratio.

For example, a data centre using 50,000 kWh of energy, with 40,000 kWh used on IT equipment, would have a PUE of 1.25.

DCiE reverses the formula:

IT equipment energy / total facility usage = DCiE.

In the previous example, the data centre would have a DCiE of 80 per cent.

 

How PUE and DCiE help you manage costs

Calculating these metrics is incredibly useful. The higher the PUE calculation, the less efficient a data centre’s energy usage is. Conversely, the closer the PUE is to 1, the more efficient is its usage of energy.

A data centre provider should use PUE to drive continual improvement in energy efficiency and, ultimately, make the data centre more cost-effective.

How to use PUE

Data centre management should regularly measure their PUE. Energy usage can vary with the time of day and season – taking regular measurements helps overcome these fluctuations. Over time, these results show how companies have improved and create future data centre benchmarks.

According to the Uptime Institute, the average PUE value was 1.57 in 2021, meaning data centres used around 60 per cent of their energy consumption on IT equipment. This is a slight improvement to 2020’s score of 1.59 – but a significant gain from the 2007 average score of 2.5. By collecting PUE over time, data centres can prove their efforts to reducing PUE.

How to reduce PUE

Reducing PUE makes a data centre more economical and provides an advantage over less efficient competitors. There are several ways to reduce PUE.

Cold Aisle Containment - Cold aisle containment counts as the largest contributor to the PUE improvement in combination with by pass air flow avoidance (blanking plates, by pass air etc)

Enhanced cooling technology - Much of a data centre’s energy is spent on cooling IT equipment. Whether it’s through enhanced airflow management, advanced cooling systems, or better layout, improving the cooling system can save a great deal of energy.

Make small improvements - Modest improvements add up. Using advanced power supplies, automatic lighting, and removing waste ensures that the whole facility contributes to a lower PUE.

Measure regularly - Above all, a data centre should measure its PUE regularly. Not only does this show when there is an issue, but it also provides a record of efforts and successes.

Why it’s important to reduce PUE

PUE and DCiE demonstrate how efficiently a data centre uses energy. By understanding the amount of energy spent on different processes, companies can assess how to make improvements that save money, improve service, and reduce waste. Our colocation data centres are designed with efficiency in mind. Contact us today to find out more.