olagon, to answer a part of your question, I just ran out into the garage and measured the following using my Kill-A-Watt and T.E.D.:
EVSEUpgraded Mitsu EVSE operating at "8A" measured 888W at 119.6v (strangely, 888W at 121.6v measured by T.E.D)
EVSEUpgraded Mitsu EVSE operating at "12A" measured 1348W at 118.2v (1.37kW at 121.4v measured by T.E.D)
From memory, my SPX L2 EVSE set to "16A" (i.e., whatever the iMiEV wants to draw) measured almost exactly 3kW at 240v (NOT 220v).
The difference in efficiency between 120v and 240v is probably simply attributable to the voltage drop across the input diodes in the charger: a 1.5v diode drop at 120v is a greater percentage than at 240v. Not enough to make me worry about it.
Somewhere on this forum is the charger efficiency number. Around 85% if I recall. Thus, to answer your question, take power x time x efficiency and get your energy answer. Our 16kWh (nominal) battery is (effectively) somewhat less than that and if you're really interested you might do some poking around on this forum as the answer is here, somewhere...
More significantly, some of us are interested in the overall iMiEV consumption. I kept meticulous track for 8000 miles which yielded an overall wall-to-wheels average of 4.2miles/kWh.
Hope this answers your query.
Curious as to why the question?