Incorrect. The heater should draw as much as it needs, with the rest coming from the pack. I would definitely worry about the S's range in Winter, though. Not in frigid weather- that will be the same as the heatpump-equipped cars. But in mild weather it will use almost as much juice as it does in frigid. What is your commute length, and the longest trips you plan to take with the car?
The charging cable that comes with the car (called an EVSE, because the charger is actually inside the car) may not be able to add enough charge for daily trips in frigid weather. Again, it will depend on how much you drive.
Thanks for the info. This should be fine. I work from home, so most trips are short and not every day. Going to hockey, swimming, groceries, dropping my wife off at work, taking a kid to the dentist, are all between 2km-20km round trips generally. Weekends we might need longer drives to do multiple errands, but even then it's usually less than 100km. And there are a few free Level 2 chargers scattered around the city.
I was mainly thinking about using the climate timer to defrost the car ahead of time on early mornings when going to hockey. With the heated seats and steering wheel, I'm hoping we can probably keep the cabin temperature down to 15C or even less.
Here's how I'm calculating it: Looking at the LEAF range chart, for the rare occasions it's -20C (basically worst case), I should lose about 20% of my range, and for my normal city driving that's currently 7.7km/kwh, so I'd end up with ~150km. Using the cabin heater set to 10-15C + seat heater might use another 2-3kwh? So range ends up roughly 130km-140km, and my trips are usually 15km or less, so I'll probably be ok.