This inspired me to run my own numbers. i3 is easily a 1/3 the cost of money and time for me.
The bigger battery for me wouldn't make much of a difference to me. I plug in at home and it takes so little time I just do it out of habit if I need to or not.
Data sources: my charge point charger account
http://www.fuelly.com/car/bmw/340i
https://www.eia.gov/dnav/pet/hist/Le...te_r50_dpg&f=m