[dataway]

I think when you compare the difference in fans, air sealing and radiators used in AC cars compared to non-AC the difference should easily make up for the added heat coming from a condenser.
When you think about it, AC does add some heat, but little compared to the heat the engine normally produces, the extra load is also pretty small, and the potential for reduced air flow should easily be compensated for with the larger fan and radiator.