Here is my trusty BikeE. I don't own a car, so this in my only mode of transport. I had to add the electric power assist after my accident in October which left me with a weak right leg and a limp.
Hills were never a problem before the accident but now they're impossible without the assist. It's powered by lithium ion polymer, the same as your laptop, so it's not too heavy. If you'd like more information about this system, here is a link to the guys that made it. I'm looking into a trike with this same set up.

http://www.ecospeed.net/index.html