Well,you can always install a 12 volt rooftop air conditioner - that's the easiest solution, however you'll take a huge hit in your arerodynamics unless you're installing it on an RV, bus, or van. If you've converted a Geo Metro to electric its not that practical. Otherwise it can be done, but I imagine that the motor you install to run the compressor will probably take a lot of power to run.
The Prius uses an electrical compressor. Don't know about its power requirements.
A company that does Ranger conversions, EVlion I believe, leave the factory a/c in place, and run it off the drive motor.
Compared to the power needed to move the car the electric motor driven A/C compressor is not using a lot of power. Remember you have high voltage in an electric car. eCycle sells their motor as a compressor drive for trucks that usually run off 24 volts but it can run on 12 volts at up to 400 amps depending upon the compressor load.
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice