Power Usage Effectiveness, or PUE for short, is an important metric for the energy efficiency of data centers. In 2007, Green Grid, a consortium of computer and chip manufacturers, defined this value. The PUE value indicates how efficiently a data center uses its supplied energy. The closer the PUE value is to 1.0, the more efficiently the data center operates.
In a time when energy demand continues to increase due to growing data volumes and increasing use of cloud services, optimizing energy efficiency is becoming increasingly important. Data center operators must therefore constantly work to lower their PUE value. This allows them to both save costs and minimize their ecological footprint.
PUE Calculation
To calculate the PUE value, the total energy consumed by the data center is divided by the energy directly used by the IT infrastructure. IT infrastructure includes servers, storage systems, network equipment, and other relevant devices. The resulting number indicates how much energy is used for the operation of IT systems and how much flows into other areas, such as cooling and power conversion. A PUE value of 1.0 would theoretically mean that 100% of the energy is used exclusively for IT. In practice, however, this is hardly achievable.
Significance
A low PUE value is the goal of every data center. It means that the energy expenditure for non-IT-relevant processes such as cooling or power conversion is minimal. For example, in 2017, Google achieved an average PUE of 1.2 for its data centers. This shows that only 20% of the energy is needed for processes other than IT operations. A data center with a PUE of 4, on the other hand, would mean that 75% of the energy flows into these processes.
Optimization Possibilities
Data centers are major energy consumers, and cooling is often one of the largest energy items. A data center uses about 35 to 50 percent of its energy demand for cooling. This is also where the greatest potential for energy savings lies. Data center operators often use ‘free cooling’, where they use outside air to cool the server rooms. This method does not require energy-intensive refrigeration machines and can significantly increase energy efficiency.
