PUE means Power Usage Effectiveness
The PUE is a unit of measurement to express the energy Efficieëtie of a Datacenter (compute center). You calculate the PUE by measuring the amount of energy that comes in, and dividing it by the energy you need. The ideal PUE is 1. Often, a lot of energy is needed to cool the servers, which makes the PUE many times higher than 1. There is the necessary criticism for the calculation, because the inventors of the model (the Green Grid) are not quite clear what you should and should not measure. It is currently the most widely used unit of measurement to indicate energy consumption. In The Netherlands is the average PUE 1.8, this equates to 100 units of energy used for the server, and 80 units for cooling, light, etc.
The PUE debate [YouTube] B0FSQ6u2u7E [/youtube]