PUE (Power Usage Effectiveness) is a standard measure used to gauge the energy efficiency of a data centre, so it’s worth exploring as part of an assessment of an off premise facility. However, with rising global temperatures, and more frequent heatwaves, achieving and maintaining low PUE in data centres can become more difficult. While daytime heat is often associated with cooling challenges, warmer evenings and nights are posing problems too, as lack of significant temperature drop during these periods can place continuous strain on cooling systems.
Data centre PUE during hot weather
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Cooling challenges
Measuring PUE
Introduced by The Green Grid, PUE is calculated by dividing the total energy consumed by a facility by the energy used solely by IT equipment: PUE = Total Facility Energy / IT Equipment Energy. PUE scores typically range from 1.0 (the theoretical best – with all energy going to IT equipment) to 3.0 (indicating significant inefficiencies).
Current trends reveal considerable progress in data centre energy efficiency. Global average PUE scores have dropped from 2.5 in 2007 to between 1.55 and 1.59 since 2020, according to the Uptime Institute. However, ongoing challenges, particularly during periods of hot weather, continue to test the capability of data centres to maintain optimal PUE values.
Why PUE matters – but isn’t the be all and end all
Lower PUE scores not only reflect environmental consciousness but also translate to reduced operating costs. For data centre operators, a low PUE score is a badge of sustainability, showcasing their commitment to environmental responsibility. For clients, it assures them that their IT operations are housed in a facility designed to optimise energy use, indirectly contributing to reduced carbon footprints.
So, for data centre clients prioritising sustainability, PUE becomes a useful criterion for choosing the best facility for their purposes. However, PUE does not tell the entire efficiency story and can be misleading, so shouldn’t be viewed in isolation. Sometimes, higher energy expenditure on cooling might be a deliberate trade-off to improve resilience or support higher capacity during peak demand. For instance, during heatwaves, prioritising uptime over PUE performance is often a necessary business decision.
The impact of hot weather on data centres
High quality off premise facilities are designed with energy efficiency in mind; they are purpose-built to optimise cooling, power distribution, and overall energy consumption. Many on premise facilities, by contrast, are constrained by outdated infrastructure and limited economies of scale – they are often hindered by being perceived merely as an overhead for the parent company, whereas a colocation business views the data centre as its primary asset and finances it accordingly.
But even the most state of the art off premise data centre facilities can feel the pinch during heatwaves. Not surprisingly, the heat can put a strain on cooling systems used to combat the heat generated by servers and storage devices. While daytime heat exacerbates cooling demands, the lack of a significant drop in temperature during the evening and night compounds the problem. Prolonged periods of heat place continuous strain on cooling infrastructure, requiring systems to operate extensively without respite. This increases the energy consumption of non-IT operations, negatively affecting PUE scores.
Higher ambient temperatures can also reduce the efficiency of cooling systems. Air conditioning units may need to work harder to achieve the desired room temperature, which consumes more energy. This inefficiency not only raises operating costs but can also lead to a higher PUE ratio, indicating a drop in overall energy efficiency.
Our facilities use free cooling chillers, which use the naturally cooler outside air to assist in the cooling process instead of relying on energy-intensive mechanical cooling circuits. By setting slightly higher room temperatures, the cooling systems can operate within a range that allows the free cooling circuits to be utilised more frequently to save energy whilst reducing operational costs and environmental impact.
Balancing sustainability and performance
Whilst we take pride in our low design PUE of 1.25, we recognise that this is merely one aspect of the energy efficiency challenge. We are committed to our green credentials, demonstrated through our environmental accreditations, participation in the GRESB programme, power contracts supplying 100% renewable energy, the installation of solar PV panels on new construction projects, energy-efficient free cooling systems, and much more.
Want to find out more?
If you’re looking to partner with a data centre that balances sustainability with performance, get in touch with us today to learn how we can support your business-critical IT and workloads within our efficient data centres whilst helping you achieve your ESG goals.