No college daughter on board for the morning commute today, so I tested a theory. 3 degrees, dry roads, starting on a full charge. I leave the HVAC off, and put the seat heater at one bar. Kept the gloves and the hat. In the interest of science, I did not freeze, and got to work with 3km to spare in full EV mode 
. Yup, seat heaters draw much less power than hvac. No wonder the people I see driving iMiEV's in winter time are all bundled up! They don't have the ICE backup...
FWIW, my Mazda3 GX has aftermarket heated seats installed - they get toastier than most would want (there is one spot on the passenger seat where the "sport cloth" fabric has melted
), but I love them for that reason (the heat, not the damage aspect
).
One thing I love about auto climate control is that the car doesn't start blowing cold air on me. I don't have auto climate control, and so I leave the fan completely off until I get up to temp.
...except the GX also doesn't have an engine temperature gauge
.
Point of all this is to say that 99% of my commutes (10km each way; ~15 mins) are done with the cabin heater completely off and just the heated seat on max (I turn it to low after about 8 mins since my backside roasts). I don't wear a jacket, hat, or gloves - just a suit (no tie
).
In my dad's RX400h, I know that the cabin heater will cause the ICE to stay on until the car's at temperature, and so I also typically would leave the climate control completely off. Same thing, heated seats help a lot.
...not an option with rear-seat passengers, however, unless the car is also equipped with heated rear seats.
And also FWIW, my wife, who HATES to be cold, never misses the cabin heat with the heated seats on - she actually turns the temp control to COOL in the Mazda since the seats get so toasty.
