I've recently build myself a new NAS box based on PC hardware (VIA C7-D) with a 220W power supply. Now I wanted to see how much power this thing actually consumes. For the measurement I bought a Voltcraft Plus ENERGY MONITOR 3000.
The measurements for now are:
~332kWh/year while the thing is idle ~376kWh/year during normal operation (ethernet + disks)If you take 20cent/1kWh you pay about 75Euro a year for powering this thing.