For peltiers, you have to put in an electrical wattage that is about equal to the heat (in watts) that you want to move. That is really bad efficiency.
From Here:
http://www.bry-air.com/tech-center/r...l/default.html
we see that
to convert Btu/Hr to Watts multiply by 0.293
just wildassguessing that you need 3000 btu/hr for ac that is 879 watts you need to move. The peltier will need ANOTHER 879 watts to do the work so you end up with 1758 watts which divided by 12 volts is 146.5 amps.
(ass-u-me-ing that i did not mess up the math)
And you dont even have a fan to blow the cold air yet.
If you wanted to use less btu/hr for cooling, run chilling tubes thru your seat.
Then you cool just your body, not the whole car.
Beware of frostbite if you try this.