Since you can charge at home or work, you may want to just pre-heat your car. It makes it real comfy to hop in a warm car on a cold day.
I use an oil-filled
1500 watt electric radiator on a timer. That will hold enough heat in the thermal mass for a 4 mile trip too.
I also built a
heated coat for about $5, and got a heated steering wheel cover. ($20 brand new at the store, or $5 brand new at the THRIFT store.)
Doing something like that would give you luxury heat, and you wouldn't need to run the 600 watt heater from the batteries, but you would always have it to fall back on.
I LIKE the neat tricks you can do with EVs, like running the heat before otherwise having the car on in a closed up garage. Don't try that one with a gasser!