The resistance heat does consume a bit but 1 or 2 Kw is about right unless you wear shorts and a T-shirt at 20F and expect the car roasting. Yes the seat heaters work great. 2Kw would take 5% of my 40Kw battery per hour. Yes it will go to 5Kw when initially heating the car. Initial heating can easily be done at home plugged in manually or with a regular timer to have you ready every morning before you roll.
Unlike gasoline an EV getting stuck in traffic in normal conditions actually increases your range. Stop and go 'idling' takes virtually no power. This will offset some of the additional power used for climate control. Lights and wipers are a nit.
Voltage is about 400 at full charge dropping close to 300 when empty.
Yes range suffers in the cold. If your EV has 200 mile rated range you would be a fool to attempt 160 miles into a snowstorm. Typical commute or getting groceries is a slam dunk. Long distance travel in the cold takes a bit of effort so hop in your other vehicle if needed. Or take the EV to the airport.
