[jsjohnst]

Sure, the best diesel engines get 40-45% and some gasoline engines approach 40%, but that is definitely not the norm. The average is 20% for gasoline (hence my prior figure) and 30% for diesel, which is a far cry from the average electric motor’s efficiency of around 90% in automobiles.

[darksaints]

Those are all roughly true numbers but you forgot charge efficiency: energy extracted out of battery / energy input into battery. That's also around 90% (assuming higher voltage charging, not 120v AC which would be closer to 60%). That would put total efficiency of battery electric closer to 80%.