"the new Volt offers an electric range of 380 miles"
No, it does not, that's the combined range with the gas range extender running for all but about 40 miles.
Even my '11 goes 40 miles on it's 16.0 KWH battery, so having 17.1 KWH on the '15 should add a few miles to what I get.
Also, while the average distance between fill-ups is 970 miles, you might want to mention that it is possible to drive for an entire year without using the gas engine. I use about 3 gallons a year, just for the engine maintenance that happens every 6 weeks, and because I do drive a mile or two farther than the battery will take me, once in a while. Mostly it's that the 2 gallons that's left after a year is considered stale, so I have to drive on gas for about two days to use it up before adding fresh fuel. I'm not saying that everyone can use so little gas with a Volt, but saying that 970 miles thing without saying what is possible is a little off.