Power usage effectiveness (PUE) or power unit efficiency is a ratio that describes how efficiently a computer data center uses energy; specifically, how much energy is used by the computing equipment (in contrast to cooling and other overhead that supports the equipment).
Naturally, it is not a surprise that in some cases an operator may “accidentally” not count the energy used for lighting, resulting in lower PUE.
One real problem is PUE does not account for the climate within the cities the data centers are built.
Additionally, according to a case study on Science Direct, "an estimated PUE is practically meaningless unless the IT is working at full capacity".
[10] 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.
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.
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.
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.
Based on the equation, the inefficiencies of the power delivery network (WL) will increase the total energy consumption of the data center.
[15] In October 2015, Allied Control has a claimed PUE ratio of 1.02[16] through the use of two-phase immersion cooling using 3M Novec 7100 fluid.
An unnamed Fortune 100 company has deployed over 30,000 Supermicro MicroBlade servers at its Silicon Valley data center with a (PUE) of 1.06.