You can't measure electricity used by looking at how much you put back in the pack. If you drive aggressively, you're also discharging the battery at higher currents, which reduces its effective capacity. So you could very well empty your battery by getting only 16kWh out of it, and you'll still need to charge it for 24kWh. You lost the rest in heat...
Going at 80mph uphill, you'll easily be pulling 40kW, and you'll be at 80kW for a while to get to that speed... That's almost 2C and 4C discharge rates, fairly high for the battery.
1st Leaf Order (order made and confirmed on 08/31 10:40am)
Delivered on December 11th 2010
15000 miles so far