Using numbers associated with running a Leaf over the last 6 yrs - 400km at 7km/kwh is about 57 kwh. 57 kwh at $0.14/kwh is $7.98 - call it $8 for 400 km. That overnight rate must be pretty good.
Some day I may upgrade to a 60kwh battery :-)
Yeah the overnight rate is about 1/3 the peak rate and they are going to make it even lower to incentivize overnight charging.