A "Whoa!" Moment

I was happily reading along in Energy Outlook, a blog about energy technology, by Geoffrey Styles when this quote brought me to a stop:

It's sobering to think that the advanced battery pack for GM's highly-anticipated Volt plug-in hybrid will hold the energy equivalent of just a half-gallon of gasoline, though the car's electric motor will use that energy much more efficiently than an internal combustion engine would.

He goes on to point out that you only get 20% efficiency in an internal combustion engine, assuming you get 80% efficiency in an electric motor, then you would turn that half gallon into a two gallon equivalent. Assuming you recover 25% your energy through regenerative braking, you are up to 2.5 gallons. I guess that is why they talk about "short haul" trips. Even at 100 miles to the "gallon", the Volt would be limited to 250 miles before refueling! But all those calculations are optimistic.