[travisb]

Mostly the latter.

Some of it comes down to the rocket equation because it takes a lot of energy to warm a battery up. If that energy has to come from a battery itself, then the vehicle needs even more battery. Carrying around that extra battery all the time will consume even more energy. And you lose about 8% total electrical energy by putting it through the lithium battery.

In comparison two litres of diesel fuel with a nearly 100% efficiency can absolutely be more efficient from a full-system standpoint.