As much of the United States struggles through the end of the nasty cold spell, a thought came to mind: Is it generally energy efficient to run the heat in my car?
Let me be a little more specific. I own a Chevrolet HHR, and as far as my understanding goes, heat is provided to the cabin by means of circulating part of the coolant loop near the blower when it is demanded (this much I think I know when I had to replace the heater core due to a mysterious coolant drainage).
Now, excluding the need for electricity being provided to the blower, am I essentially being energy efficient by using the engine's heat to stay warm instead of wearing my coat in the car, or is there a separate heating element that is using more energy?