The Advanced Vehicle Research Center garage in Raleigh is one of a handful of companies that converts the Prius or other hybrids into plug-in hybrids, doubling their gas mileage. The result: A car that breaks a once-unimaginable fuel efficiency and delivers 100 miles per gallon, on average, with some drivers reaching 150 to 200 mpg under optimal conditions. The spare battery costs less than 75 cents to charge and gives the plug-in Prius about a 35-mile range solely on electric power, making gas optional on short commutes.

 
The small garage sees demand mostly from corporate customers with fleets of cars, but recently converted its first car for a private consumer. Anyone who owns a Prius and can spare $10,400 can get a custom conversion by the Raleigh garage, Charlotte Energy Solutions and other custom installers in nearby states. By the end of the year, Advanced Vehicle Research Center expects to have at least 30 such plug-ins on the road, including 20 in this state.

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