Though, oddly, as far as I can tell, the Spark EV has just 6% charging losses. Not sure why it is noticeably better. Presumably something to do with the battery architecture...
I wanted to correct this datapoint. As far as I can tell, the real charging efficiency of my Spark as measured by 1) The Chargepoint and 2) the energy-use meter in the car is:
13.8kWh used
16.49kWh from the Chargepoint.
So that's an efficiency (wall to battery) on the Spark EV of just
83.7% (Which is
worse than what I have measured for the Tesla Model 3 using a similar method - about 87-88% for the Tesla is what I have measured.) Of course, no vampire on the Spark so effectively it is probably more efficient.
I swear I checked this previously, and the result was much better, but it was a couple years ago, possibly with a less aged battery (and a different Chargepoint), so there may be confounding factors in the estimates of energy used. (My Spark EV battery has also degraded a bit - it seems to have ~16.2kWh total capacity vs. the ~17kWh when new.)
Obviously I am dependent on the accuracy of Chargepoint metering, too. (It's a free Chargepoint, so no perverse incentives, but maybe they skew their meters in their favor as a general policy.

)
But, wanted to correct the record here with the best data I have right now. I'll check again sometime, perhaps for an even more complete discharge of the battery (which could be a error factor as well).