Data centers are extremely energy and cost intensive. To evaluate the efficiency of the energy used in data centers, there are several approaches based on organizational or pure energy balances. These approaches can be used to quantify energy efficiency.
The approach adopted by The Green Grid Organization recognizes two characteristic values: the Power Usage Effectiveness (PUE) and the Data Center Infrastructure Efficiency (DCiE). The PUE value relates the total energy consumed in the data center to the energy consumption of the computers. The PUE value is thus used to determine the efficiency of energy use over a specific period of time. Longer-term trends in the PUE value are expressed in the Energy Usage Effectiveness( EUE) parameter. PUE values of 3 and above mean that the energy concept used in the data center is completely inefficient. A value of 3 indicates that two thirds of the power used is consumed for heat and heat dissipation, whereas only one third of the power used is consumed by the computer. When this ratio approaches 1, it ensures that the data center is operating extremely efficiently. PUE values of 1.3 are already excellent and mean that 30% of the energy used is consumed inefficiently.
The DCiE value, on the other hand, evaluates the efficiency of the energy used in the data center. The two values are calculated from the total energy used and the power of the IT equipment. Whereby the Power Usage Effectiveness is calculated from the quotient of the total energy of the data center to the energy consumption of the IT devices. DCiE is the reciprocal of PUE, i.e., 1/PUE.
Includedin the total energy is the energy for the switchgear, uninterruptible power supply( UPS), batteries, etc., and also the energy for the cooling, air conditioning, and that for all IT equipment, for computers, storage, telecom and peripherals. As for cooling energy, this is included in the PUE value as a subset, Water Usage Effectiveness(WUE), as is the energy balance for carbon, which is expressed in the CUE value, Carbon Usage Effectiveness (CUE).