What is Power Usage Effectiveness?

Power usage effectiveness (PUE) is a way to measure how efficiently a data centre uses energy. It is calculated by comparing the total energy consumed by the facility to the amount used by its IT equipment.

First introduced in 2007 and backed by The Green Grid, PUE is now widely recognised as the global standard for measuring data centre energy efficiency, and plays an important role in assessing data centre providers’ environmental impact and corporate responsibility.

How to calculate PUE in data centres?

Calculating power usage effectiveness involves two key elements:

• The IT load, which includes the energy used by servers, storage and networking equipment. It is typically measured at the power distribution units (PDUs).

• Total facility energy consumption, which includes all energy used across the site, for example, cooling, lighting and backup systems. It is usually measured from the utility meter.

The formula for PUE is: Total Facility Energy Consumption ÷ IT Equipment Energy Usage = PUE.

Let’s look at an example. If a data centre uses 120,000 kWh in total energy and 100,000 kWh for IT equipment, the PUE is 1.2.

Lower PUE values reflect more efficient energy use as they indicate that a greater proportion of the facility’s total energy is going directly to powering IT equipment rather than being lost to cooling, lighting or other infrastructure overheads. This efficiency not only reduces waste but also helps to reduce energy costs and lower overall environmental impact.

PUE and data centre energy usage

Modern data centres power the digital infrastructure behind industries ranging from finance and healthcare to media and retail. As demand for data and connectivity grows, so does the energy required to keep servers, storage and networking equipment running. These systems generate heat, making efficient cooling and space management essential to maintain performance and avoid downtime.

PUE plays a key role in tracking how efficiently a data centre uses energy, offering a clear measure of how much power goes directly to IT equipment versus what’s used for supporting infrastructure.

What is a good PUE?

The best possible Power Usage Effectiveness is 1.0, which means all energy consumed by the facility is used solely to power IT equipment with no waste from cooling, lighting or other infrastructure.

According to the Uptime Institute Global Data Centre Survey, the industry average for PUE in 2023 was 1.58, with larger facilities typically achieving better energy efficiency, often because they are relatively new and use more efficient cooling technologies and more sophisticated control systems.

How to reduce PUE?

Lowering PUE is one of the top priorities for leading data centre providers, including Telehouse, and it requires a mix of strategic upgrades and ongoing optimisation.

One of the most effective methods is Cold Aisle Containment, which separates cold and hot air streams to maintain efficient cooling. When paired with bypass airflow management, such as blanking plates and optimised floor tile placement, it can significantly cut down on energy waste.

Switching to high efficiency cooling technologies, improving airflow and designing smarter layouts can make a noticeable difference. Even small changes like using energy-efficient power supplies, automatic lighting and tightening up energy waste can add up.

Lastly, it is important for data centre providers to regularly monitor PUE. Continuous measurement helps identify inefficiencies, track improvements and refine strategies. For colocation providers, it’s a key step in delivering efficient, environmentally responsible data centre services.

While PUE is a widely used metric, it’s not the only one. Other indicators, such as Water Usage Effectiveness (WUE), Carbon Usage Effectiveness (CUE) and Energy Reuse Effectiveness (ERE), also play an important role.

How does Telehouse achieve a low PUE in data centres?

Telehouse is actively working towards improving the PUE of its facilities through several targeted upgrades across our electrical and mechanical systems, which included replacing outdated UPS systems and legacy Glycol pumps with modern, energy-saving models across Telehouse North and East buildings.

In 2024, the Telehouse West building underwent significant improvements with the installation of new air-cooled chillers featuring free cooling technology, built to operate efficiently even in extreme temperatures. Across the data halls, a series of updates, including the introduction of Cold Aisle Containment and in-depth thermal analysis, have helped optimise airflow and cooling performance.

If you’d like to learn more about our data centre services or our commitment to driving power usage efficiency, get in touch with us today.