We used the WattsUp? Pro meter in these tests, which allowed us to measure power use directly from the wall. This meter also uses a USB cable to connect to a computer, and Logger Pro software to graph the readings while we run our tests.
To test total system power use, we used AIDA64 Stability test to load the CPU, and then recorded the results.
Here, we can see the results of our power tests, with the Xeon E3-1285v3 showing the lowest power use. There is about 20 watts difference between the two at idle.