There is a company called Hymotion which has developed an add on for Hybrid Electric vehicles such as the Toyota Prius, Ford Escape Hybrid and Mercury Mariner Hybrid which allows these vehicles to plug into an outlet over night and drive 50 miles further on an electric charge.
According to Hymotion, “A Customer Survey indicated that people preferred plugging in a vehicle instead of going to the gas station. Hymotion PHEV system can average more than 100 miles per gallon. And if used only for short trips, 500 miles per gallon is possible. At 100 mpg, it could cost the equivalent of only 75 cents a gallon to operate and it needed to go to a gas station only every other month.”
The company’s FAQ states that they anticipate selling to consumers in October of 2006, although units are currently available for government and fleet use.