[mikeash]

The battery makes a big difference. Since it's just a helper on the regular Prius, it doesn't have to be all that powerful, and I think it's only rated for something like 30-35hp. On the plugin, it needs to be able to drive the car on its own in a reasonable fashion, so it's much more powerful, as well as the obvious thing of having a higher capacity.

Driving my Prius v, I'm battery-only basically when cruising on surface streets, sitting idle, or maneuvering around small, slow residential streets. And maybe, maybe if I'm accelerating away from a stop on a decent downhill slope with nobody behind me.