Is that accurate?

Well if you count expected power consumption of each component and limited efficiency of the power supply, plus reports of people idling their 3470 based machines at 12w (full system) yeah, good enough. I mean what is your point? The 35W idle for Ivy Bridge CPU only is a ridiculous claim, that should be retracted IMO.

CPU and mobo sensors are accurate enough for casual measurements and conversations like this.

The numbers I cited earlier were reported by the CPU's package power sensors which were in turn read by LibreHardwareMonitor.