JoeS wrote: probably more due to instrument tolerances, although maybe the newer i-MiEV might have it's power draw dialed down slightly.
These power meters are much more accurate than the 14% difference between 12A and 14A.
EKM Omnimeter accuracy class 0.5%
However the Efergy sandage used may be off by a lot, or could be accurate to 1% if the voltage is measured and input into the device...:
You have to measure the voltage and then program it into the device. Power factor is not taken into consideration. This is not a super accurate device but is good enough to give you a ballpark measurement for home use.
They don't have a voltage connection and therefore do not sense voltage. Voltage is entered in the display. These are really current meters that don't measure kw or even volt X amps. The accuracy will be very bad with motor and transformer loads. Also inaccurate with voltage changes.