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If you want to be fair all the energy going into the system should be used to figure fuel economy.

I couldn't agree more. But gasoline is only roughly 25% efficient at turning thermal energy into motion, whereas electricity channeled thru a motor is closer to 90%.

Even if you factor in power line losses and battery charge&discharge losses, it's still well above break-even in power loss, since the fuel also has "losses" in terms of refining, distribution, storage, and retailing.

Fossil fuel,however, is a limited resource and will continue to go up in price as the energy expended to obtain it goes up and demand rises above supply. Electricity is made from various resources that it is not feasible to make gas out of, but is plentiful and cheap... like hydro and nuclear.. and in the near future, solar & wind.

Even when electricity is coal-generated it is still cleaner than burning cars in individual engines:

CalCars initiated efforts to promote fleet purchases of plug-in hybrids to be built by automakers, and documented the emissions benefits of plug-in hybrids not only on California's clean power grid but also on the national (50% coal-fueled) power grid.

Maybe the best indicator is how much the cost difference to drive a hybrid 50 miles on electricity is compared to the cost for fuel... fuel is about $2.50 now (according to the news... and almost 3. in California), and electricity about .15/KW-Hr (this varies a lot. My hometown utility sells at about .08/KWH, most of it from hydro.)

There's about .75 KWH per HP-Hour, so figure it costs 10 KWH to drive 60 miles (assuming power to maintain cruising speed is 10HP- I don't know exactly, but for a car with a CD of .26, it sounds very reasonable)then you are paying .15* (about 8)KWH=about $1.20/60 miles. You could also assume that the cost of electric power will go up, as some is natural gas, and the cost of producing electricity from NG and coal will also go up. I can't see electricity doubling in cost, but I CAN see fuel going up another $1/gallon.

PS The battery pack in the Prius is 100-130 pounds. Depends on model.
Little known fact: the International version of Prius has a "stealth" button that disables the gas engine entirely. The button is disabled in US models, but the function is still there, waiting to be exploited!
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