An idea to think about: A removable 'trunk' that contains a generator and fuel that has the ability to produce 75% of the energy to run the car (if it takes 100kw per hour, generate 75kw). Have this kick in when the battery hits 50% charge. Use the weight reduction to increase battery size which will increase electric only range. Aim for 60 miles. On days that one is traveling less then 60 miles, leave the 'trunk' at home. If you are going more then 60 take the 'trunk', and you should get around 100 miles of range. If you are running in the city you will get a lot more range as there are all those stoplights and traffic jams to charge up during. The trunk can also be shared between cars, so one per family (assuming they have the same model car, or some smart company makes a universal connection)