TUE or not TUE? Cundall latest to question efficiency metrics

20 September 2021 | Melanie Mingas

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The use of PUE in measuring data centre efficiency has been called into question by Cundall, the international multi-disciplinary consultancy that has delivered a portfolio of green buildings, including the Facebook Odense Data Centre.

Critical systems partner Malcolm Howe said that power usage effectiveness (PUE) is "an incomplete metric" because it considers only the power delivered to the rack, rather than the use to which that power is put, i.e. cooling, computing or other uses. Instead he said Total Power Usage Effectiveness (TUE) should be used as a basis to better understand how efficient a facility is.

Pushing for the data centre industry to consider new metrics, designs, processes and actions in its shift to more sustainable operations, Howe wrote a blog post exploring the topic.

It read: "Specific to each individual data centre and influenced by a range of different factors, PUE does not provide a reliable platform for comparing one facility to another. Neither does it give a good indication of environmental performance, although it has often been used in this way. Rather, PUE provides trend data whereby efficiency improvements at a particular site can be monitored for their relative effectiveness."

The piece was published only days after the Uptime Institute said energy efficiency in data centres had flatlined. 

The firm said that, following the IPCC's report on global warming last month, "now is the time for the data centre industry to seriously consider new metrics, designs, processes and actions if the industry is to achieve sustainability targets, such as, net zero emissions in the timescales announced".

To replace PUE, Howe recommended a new equation: multiplying ITUE – a server specific value – with PUE – a data centre infrastructure value.

Howe wrote: "Although TUE has been around for over 10 years, it has gone largely unnoticed and unadopted by a large percentage of the industry. Yet the metric holds the possibility of a more precise indication of overall data centre energy performance. Whilst the debate continues about creating new metrics, raising awareness of TUE, and promoting it as an industry benchmark standard for data centre energy efficiency, could be very valuable in helping data centre operators implement improvements in performance."

However, it's not just about measuring but also reducing the energy load. Howe said that in addition to energy efficiency metrics and cooling solutions, hardware design practices also need to be challenged.

Dozens of data centre players have announced new or enhanced sustainability targets over the last 12 months, with some now working towards a hard deadline for net zero emissions. Recent announcements have been made by Colt, Vantage, O2, Amazon and Facebook while Google upped its water reduction targets only this month.

Elsewhere in the ICT industry, Vodafone now runs its European networks with 100% renewable energy and Orange this year boosted its use of solar across the MEA region as it works to a 2040 zero emissions deadline.