Here's a completely unscientific but real world response based on my personal observation...
Today I had a busy day. Busier than usual. I drove to town. I went to Lowe's, Costco for gas, the grocery store, the dentist, and a sporting goods store. I stopped and had lunch at Burger King, then I drove back home. Like I said, this was a busier day than usual. I drove 31 miles and burned about $8.50 worth of gas in the process. So give me 40, or give me 28 miles, I don't care. If I had the Volt today I would have used about 80-cents worth of electricty at my utilities current rate. I would have saved $7.70 and gotten everything done that I needed to do.
Today I had a busy day. Busier than usual. I drove to town. I went to Lowe's, Costco for gas, the grocery store, the dentist, and a sporting goods store. I stopped and had lunch at Burger King, then I drove back home. Like I said, this was a busier day than usual. I drove 31 miles and burned about $8.50 worth of gas in the process. So give me 40, or give me 28 miles, I don't care. If I had the Volt today I would have used about 80-cents worth of electricty at my utilities current rate. I would have saved $7.70 and gotten everything done that I needed to do.