Some tip:
It won't reduce your bill however it will take care more of your battery.
15 minutes before you leave your garage put the heater with the remote app, it doesn't matter which temperature, for example you can set at 70F, once the cabin reaches 70F it will consume very little to keep the cabin warm, however the heater will start also the heating of the battery as well, this process will use energy from the wall and not from the battery, so when you leave you have a warmed battery, make sure your car always is plugged to the wall.
It won't save energy (just a little, the saving is avoiding the loses about sending the energy from the wall to the battery then the battery to warm the battery) however the advantage of this step is that you will pre-warm the battery with energy from the wall and not from the battery itself, it increases longevity of the battery, also you will have about 8 or 10 extra miles to drive since they won't be consumed to warm the battery the first time.