According to fueleconomy.gov, save $416 annual fuel but you pay $11,000 more for adding battery from the Escalade non-hybrid. is it worth? Think about it!
I agree with both Stephen and Bob, if your going for a "green" car, buy a small toyota or the new honda hybrid civic (pretty fancy stuff that car is). Also, unless your going to have the car for over 10-15 years, youll be losing substantial money.
Hope this helps