I've had my new Chevy Volt for about 3 weeks, now, and I've been keeping track of its fuel efficiency. The standard seems to be to compare kilowatt hours (kWh) per 100 miles to gallons per 100 miles. Here's what I find so far.
My utility charges about $.095 per kWh hour, and I am using 33 kWhs per 100 miles. That is an astonishing $3.14 per 100 miles. By comparison, my neighbor has a Nissan Murano, the fuel efficiency of which lists at about 21 miles per gallon. The average price per gallon in my state currently is $3.41. He is spending about $16.24 to drive 100 miles. That's a difference of $9.83 per 100 miles.
If I compare the same fuel efficiency to my late Honda Insight (sniff), which got 62.2 miles per gallon, I still save quite a bit - and the Chevy Volt is a much nicer car. It cost the Honda about $5.48 to travel 100 miles, so I am saving $2.34 per 100 miles, compared even to the Insight.
I have used some gas in the Volt on a couple of small trips. The gas engine is actually a generator, which charges the battery as you drive - so the electric motor still drives the car. Over the life of the car, so far, I am averaging 105 miles per gallon. That will inevitably rise, since most of my driving requires electric energy only. I have to keep in mind, however, that I will have to use gas on occasion, so that the gas in the tank doesn't get too old. On the two occasions that I have put gas in the Volt, I didn't fill it up. The most I put in was 4 gallons. It does use premium ("Top Tier"), which cost (at the time) $4 per gallon. That came to $16, and I haven't put $30 worth of gas in it since I've had it.
I have finally gotten around to taking some photos, and I have changed my icon. You can see my Volt by clicking on my icon.