Ponca City, We Love You writes "For $12,500, OEMtek says it can add a battery-range extender to your Prius and double its mileage to 100 mpg or more. The change involves installing a 200-pound pack of lithium-phosphate batteries with six times greater energy storage (pdf) than the Prius' original hybrid battery, which remains in place; software; a dashboard read-out; and a 110-volt outlet. Company literature claims "you can drive 100+ MPG." OEMtek says its converted Prius will be capable of 30 miles of all-electric driving, and that it has achieved 147 mpg in city driving and 102 mpg on the highway. Both Toyota and General Motors have said they're working on plug-in hybrid cars, aiming to put them on the road around 2010 or 2011 but Cindi Choi, vice president of business development for OEMtek, doesn't see this as a short window of opportunity to convert Prius models. "There have been over 1 million Priuses sold globally. That's a large market in itself," says Choi."