capacity". All in all, finding simple, yet recurring issues such as the problems associated with the effect of varying temperatures in cities and learning how to properly calculate all the facility energy consumption is very essential. By doing so, continuing to reduce these problems ensures that further progress and higher standards are always being pushed to improve the success of the PUE for future data center facilities. To get precise results from an efficiency calculation, all the data associated with the data center must be included. Even a small mistake can cause many differences in PUE results. One practical problem that is frequently noticed in typically data centers include adding the energy endowment of any alternate energy generation systems (such as wind turbines and solar panels) running in parallel with the data center to the PUE, leading to an obfuscation of the true data center performance. Another problem is that some devices that consume power and are associated with a data center may actually share energy or uses elsewhere, causing a huge error on PUE. Benefits and limitation PUE was introduced in 2006 and promoted by The Green Grid (a non-profit organization of IT professionals) in 2007, and has become the most commonly used metric for reporting the energy efficiency of data centres. Although it is named "power usage effectiveness", it actually measures the energy use of the data centre. The PUE metric has several important benefits. First, the calculation can be repeated over time, allowing a company to view their efficiency changes historically, or during time-limited events like seasonal changes. Second, companies can gauge how more efficient practices (such as powering down idle hardware) affect their overall usage. Finally, the PUE metric creates competition, “driving efficiencies up as advertised PUE values become lower". Companies can then use PUE as a marketing tool. However, there are some issues with the PUE metric. Rather than the issues mentioned in the last paragraph, some other issues are the efficiency of the power supply network and calculating the accurate IT load. According to the sensitivity analysis by Gemma, "Total energy consumption is equal to the total amount of energy used by the equipment and infrastructure in the facility (WT) plus the energy losses due to inefficiencies in the power delivery network (WL), hence: PUE=(WT+WL)/WIT." Based on the equation, the inefficiencies of the power delivery network (WL) will increase the total energy consumption of