At what temperature does it force you to use gas?
I have a Chevy Volt and it performs in a similar fashion related to heat. You have electric heat down to 35F or 15F (depending on your preference). Below that it forces the gas engine to run periodically.
When the temperature is below freezing...
That is basically the same programming as the Chevy Volt. You have HOLD mode (Save) and Mountain Mode (Charge). Although in the Volt, Mountain will only let you charge up to about 40%. This allows you to ensure you have plenty of power in reserve should you have to climb up a mountain.
I'm...