I know my undvervolted Celeron 420 uses about 10 more watts under load than at idle, measured at the plug. Since it is powered solely off the 12volt line, that's less than one amp after the efficiency of the PSU is taken into consideration. Given VRM losses, it's probably 6-7 watts of real increased power consumption under load. Whole rig idles at 40 watts with the hard drive on standby. 47 watts hard drive on. While gaming using IGP I'll see up to 60 watts consumed.