Cost savings from plug-in hybrid

The New York Times just reported on a couple of plug-in hybrid vehicles, such as the GM Volt and the Tesla Roadster. One interesting fact is that the Tesla gets approximately 100 miles per 32 kilowatt hours (kWh). So how would your annual fuel cost vary between a 25MPG conventional gas engine and the plug-in? The chart below compares annual fuel costs for someone who drives 12,000 miles over a range of electricity and gas prices.

As of today, I'm paying $0.14/kWh for electricity and $1.75/gal for gas, so my annual costs would be $538 for the plug-in and $840 for the conventional. With $300 savings per year, it is hard to justify the price premium on a plug-in (the Tesla is over $100,000, the Volt is estimated to cost over $40,000). Of course, fuel is only one part of the total cost of ownership for a car, and plug-ins may become cheaper as the technology matures.