Though the Volt can go as far on 1 gal as it could on 13.6kWh, how far could it go on gas if it weren't a PHEV? The battery weighs 375lbs, the motors aren't light either, and weight added at the design level compounds with heavier components throughout the design.
Also, the Volt is big on the outside, but small on the inside, on account of the passengers having to share space with a battery. This gives the Volt utility comparable with a smaller car. From another perspective, the bulk of the battery is an aerodynamic penalty.
Anyway, running some numbers through
this spreadsheet, I find that just knocking the battery down from 375lbs to 50lbs would boost fuel economy to 40mpg, and cutting a 3.5 inches out of the middle of the car and ending up with a smaller hybrid (with the same utility and interior space as a Volt) that weighs as much as a regular Cruze would bump fuel economy up to a respectable 45mpg. It would also bring the price out of the stratosphere and in to the low $20k's, resulting in greater adoption and more total benefit to society at this time.
So, for a vehicle with the interior space of a Volt, a PHEV variant would get 368Wh/mi, and a HEV variant would get 45mpg. In other words, 16.5KWh takes you as far as 1gal. Per the metrics derived in the first post, the two methods of travel have a CO2 footprint that is
equal. Looks like Dr. Samaras knew what he was talking about.
If you have a certain number of dollars to spend on environmental concerns, you'd be
wrong to spend them on vehicle electrification before you first work on reducing the carbon intensity of your electric supply. The same goes for time you spend advocating for environmental causes.