http://thefraserdomain.typepad.com/energy/2007/04/new_engine_desi.html#comment-65344338

Average mileage is the key concept with plugin hybrids. The average trip length between overnight recharge is 23 miles.

So if enough battery capacity is installed to cover around 25 miles, that means that every trip up to the average length uses no liquid fuel. Providing the vehicle has enough power in electric mode alone.

For that the drivetrain needs an electric motor powerful enough to provide full performance. A paralell hybrid like the Prius has a smaller electric motor that is only powerful enough to drive up to 35 mph. the paralell hybrid relies on a combination of electric and ICE to attain full performance.

A serial plugin hybrid is designed with a more powerful electric motor that handles full performance alone.

So to boost average mileage to 250+ mpg a serial plugin hybrid is needed. Overnight recharge is fine, it uses cheaper batteries and does not need special quick charge "gas" stations.

Consider this typical example of my driving habits to understand how this very high average mileage would occur. On work days my drive is under 25 miles round trip. On one weekend day it is 25 miles again.

On the other weekend day I drive 55 miles between charging. So after the 25 mile battery range I have another 30 miles. Acomplished by using 3/4 of a gallon of liquid fuel. (biodiesel in a backup generator at around 40 mpg).

So my mileage over the week is 205 and I used 3/4 of a gallon of fuel. That is 273 mpg.

Now consider an sofc/microturbine backup generator that gets 4 times the mileage of the diesel generator. 3/16 of a gallon of fuel for the 205 miles. 1093 mpg.

Renewable electricity to charge the batteries would emit no carbon and cost the equivalent of 60 cents per gallon of fuel. And no wars would need to be fought to obtain that electricity, unlike oil based transportation as we know it.

Serial plugin hybrid technology, sofc/microturbine generators, and renewable electricity. The complete solution to GHG disaster and perpetual oil war.

Not to mention it would revive our economy by cutting the huge deficit and war debt incurred in the process of obtaining foreign oil. It would even revive our manufacturing base if this technology was mass produced here in the US.