My wife complained every day when she saw the low fuel light when I drove for 2 weeks with a single gallon left in the tank. She said she would call the news reporters if I ran out of electricity and gas and ended up stuck on the side of the road, so I decided to purchase 3 gallons of fuel to shut her up ;) As it turns out, with the Volt, to end up on the side of the road, you have to run out of your initial electric range, run your gas tank dry, and then it gives you one final chance with about 10 miles of range in reserve electricity. It truly takes an idiot to end up on the side of the road with this car, or someone in a really bad situation. I have burned maybe a half a gallon of 3 gallons added that was pumped in exactly a month ago.
The next two pictures are data collected at voltstats.net. Voltstats uses an On-Star API to poll my car multiple times throughout the day to gather usage data. This is actual data from my car and is precisely accurate. I found out about voltstats a few weeks after I purchased the car. As a result, you will notice the data collection starts after I had already traveled a few hundred miles.
The Green in this graph represents electric miles. The Blue in this graph represent Gas Miles, or what is known as Charge Sustaining miles, since the gas motor is used to keep the battery charged at 30%. If you notice, the blue hasn't increased much at all in this graph. I have been traveling about 70 miles a day round trip to work.
This graph is my monthly MPG. January is the lowest as the weather was cold, and I would generally run out of electric range about 2 miles from work (I would get about 33 miles of electric range). I would burn about .10 gallons of gas to go 2 miles. I'm not sweating the 300 MPG, however. As you will notice, I achieved over 800 MPG in February, and in March, and I haven't burned any fuel whatsoever. I am averaging about 45 miles of range in average temperatures of 63F. Voltstats seems to record no fuel burned as 999 MPG.
This picture is a snippet from my electricity bill. There are a lot of variables that go into an electric bill, but I am posting this so you can see that the car hasnt spiked my usage. I am comparing the first two months of having the car to the previous year without the Volt.
My lifetime MPG is currently exactly 350 MPG. It is going up every day as I 'work off' the first week of a lot of gas driving. I expect to be over 500 MPG by the end of March.
I am using 34 kwH per 100 miles traveled. This number actually takes into account the total amount of energy required to replenish 10 kwH of of usable charge. This number is normally around 13 kwH.
To calculate what your electricity would cost, take the electric only miles you plan on traveling in a year, and divide by 100. Take that number and multiple it by 34. Take that number and multiple it times your electric rate. For me:
22,000 miles / 100 * 34 * .06 cents=$449. That means I will spend about $449 to travel 22,000 miles. If you were driving a regular car, $449 would get you about 119 gallons at $3.75 a gallon. If your car got 30 MPG, you would go 3592 miles. That means the Volt can go about 6 times the distance for the same money in fueling cost.