I had the heat on in my car this morning because it was cool (spring-like weather for the rest of the country, but cold for Texas - 40 degrees). I had the heat on from the moment we left to take the kids to school until the moment I returned sans kids. I then got out of the car. The temperature was warmer out of the car than it had been in the car with the heat running for half an hour.
I hate my car.