[terry1156]

I'm not a car expert, but I think you're right. Heat comes off the car engine so it uses little if any extra energy. AC is a little different. If you are speeding down the highway at 70 mph with the windows rolled down, then AC is probably better. But open vents would be better than AC at that speed. For everyday town driving at lower speeds, windows down probably save money over the AC, with vents still being the best.