It's not just a matter of if it's economically viable.. it's a matter of the amount of energy returned, on the energy that's invested in it..
If it takes more energy to make it, than we get from it.. then all the energy it produces simply goes back in to getting more.. and none of the energy makes it to market..
Okay.
Economic viability doesn't matter.
Hybrid vehicles are not the end-all, beat all. In fact, I predict Hybrids will be ridiculed in a few years.