This might help you:

http://www.gaussianwaves.com/2010/01/calculating-power-and-energy-content-of-a-signal-in-matlab-2/

Hi Fatmir,

What are the type of machines ? Are they solely three phase and single phase AC motors ??

You need to obtain the timing schedule for running (including details of start/stop) and loading separately for the machines, as a first step.

-Sanjay

http://www.slideshare.net/mafazahmed/calculating-the-efficiency-and-regulation-of-transformer-using-matlab

This is one write the M-File code used for calculating efficiency for transformer it may help with you