A large battery pack and a charger are installed in the car below the rear deck.  No original components in the vehicle are modified and storage space is not impacted.  The charger plugs into a regular 120v outlet and fully charges the additional battery pack in about 5 hours.  When charging is complete the car can be driven up to 25 miles without the engine turning on at speeds below 35mph.  At higher speeds the electricity that was stored by charging the additional battery pack blends with the gasoline powering the engine to produce much higher mileage than an unmodified vehicle.  When the additional battery pack is empty the car reverts to original operation automatically.  (See mileage charts below.)