Conquered PUE? Consider CUE and WUE Next

February 10, 2016

CDW Dual Row of TeraFrame CabinetsPower usage effectiveness (PUE) is the leading metric used globally to measure the amount and efficiency of power used in data centers. The PUE is calculated by dividing the total amount of energy used by the data center by the amount of energy used by its IT infrastructure, without considering other factors such as lighting, cooling, etc. An ideal data center would have a PUE of 1.0. 

However, a low PUE doesn’t necessarily mean a data center is environmentally friendly, as this article explains. Simply put, while a PUE can give us a good idea of how efficiently a data center uses the energy it consumes, it offers absolutely no insights into how much carbon emissions the data center is responsible for or how much “greener” one operator is than another.

That’s why the Green Grid Association has come up with the carbon usage effectiveness (CUE) and water usage effectiveness (WUE), both of which can create some challenges when designing a data center.


CUE factors in carbon emissions generated through data center operations. It is calculated by dividing a data center’s total energy-related carbon emissions by the power used to drive IT, or by multiplying the PUE by the data center’s carbon emission factor (CEF), which is the amount of emitted carbon dioxide (or carbon dioxide-equivalent) in kilograms per kilowatt-hour. 

WUE helps determine the amount of water used by the facility and the efficiency of that usage in IT operations. This metric is a ratio of the annual water usage to how much energy is being consumed by the IT equipment and is expressed in liters/kilowatt-hour (L/kWh). 

As computer densities increase, it is important for managers to take examine their data centers and find solutions for maximizing smart, efficient, and a low-impact use of resources.

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CJ Castillo, Technology Writer

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