You're certainly in really cold weather so using heat is more necessary. For me here the average temperature is in the 30's so many times I can get away without heat easily and other time I just have to dress warmer and still make it.
I found my engine will not run in as cold as 0F or above, but once the temp dipped below zero (one day it was -10 to -7F during a drive), the engine started to charge the battery 1/2 way through the trip and charge on the battery. On the way home in the afternoon it was 17F and a very "easy" drive home for me compared to the negatives on the way in the morning.
No worries about battery warmth, the cold will not hurt it. It won't be able to put out as much high demand energy (full power), but I never drive more than 1/2 power demand anyways. Its the stiffness of the car, wind resistance and such that shortens the range in the winter by a much bigger factor than the cold battery. You can certainly notice the stiffness, the car won't coast nearly as long or far in cold weather and the MPGe numbers can go down by close to 85 from best case in the summer around 210mpge for me to worst case in the winter around 125mpge for the same trip.
Edited by rbort, 15 September 2016 - 06:11 AM.