I use the Silo at 13 watts. I used to be a volts guy because I had a 2.5, which I sold in July I think for my Reo. I've picked up a couple more VV/VW devices and just became more familiar with the wattage measurement, so I use the P3 on watts. It's just two different ways of measuring the same thing more or less.
Especially since getting into mechanicals, I measure what my builds are doing based on the watts, because the voltage is essentially a constant variable with mechanicals.
The P3 rocks though! still trying to land on a good high end topper for it. Erlkonigin has been a miserable fail, and I'm in the market for a Squape-R now