In an ICE, the wasted heat (there's plenty to go around!) is dumped to the cabin for heat. The temperature of the cabin is generally controlled by the mixture--or amount of this waste heat being mixed with ambient air to control the cabin temp. So temperature is essentially controlled by adjusting the mixture of hot air instead of the temperature of the hot air itself. Maybe it's just me, but when I have the cabin temp in the Model S set to the low 70Fs, the air doesn't seem to get very warm. It seems to never get the cabin comfortable. But if I crank it to the mid to upper 70Fs, it definitely does and the air feels significantly warmer. So is the heat pump actually working harder to generate warmer air at higher temperature settings, or is the car just mixing less ambient air at higher temperatures? In other words, is the heat pump simply on or off? I ask because it seems like there's a bug--I drove to work in 30F weather this morning, and with all settings on auto and the cabin temp set to 72F, it never seemed to reach the desired steady state temperature. 74/75? Now we're talking. But 74F would make me uncomfortably hot in a room. Maybe the internal temp sensor just isn't calibrated right.