Does the heater really use all that much energy? A home space heater is something on the order of 1 kW, which is a fraction of a percent of what is needed to move the car.
The climate control in my (non-tesla fwiw) EV with a heat pump uses around 2kW when its going full-out. Anecdotally it also heats the cabin much faster than a space heater would.
Usually it's only pulling that much juice for the beginning of a drive and after a few minutes it reduces when it finds a steady-state.
2kW is about the same amount of juice that the drivetrain pulls when driving 35mph, so it can make a pretty big difference in the efficiency of shorter drives.
Sidenote: even though resistive heating is less efficient in heat per watt, using the heated seats is usually more efficient in terms of comfort per watt than heating the entire cabin
>A home space heater is something on the order of 1 kW, which is a fraction of a percent of what is needed to move the car.
How are you getting "fraction of a percent of what is needed to move the car"?. Wikipedia says the model 3 (long range, RWD) has 82 kWh capacity and 363 mi range. If you drive at 40mph that's 9hrs of driving, meaning the car consumes 9kW at that speed. 1kW is not "fraction of a percent" of that.
Yes - for a non-heat pump it's 2-3kw, all-in.
The car is not using more than ~10kw, all-in.
Today, it's closer to 1.5kw, all-in, accounting for heat pumps, etc.
Cooling is less intensive.
Keep in mind:
Homes are also often well-insulated, at least, much more so than a car. Most car insulation is designed for noise/etc, not for temperature control. The glass is usually R-1 or worse.
So if you want realism:
My wife's office, no more than 150 sqft, built in 1923, and with no real insulation in the walls (and no space for it), and a bunch of older windows, can't be kept at 68F by a 1500 watt space heater running 100% of the time on a cold day (IE 30deg F).
This is in GA, so not exactly a super-cold climate, eiher.
Meanwhile, my workshop, same property, built a few years ago, 2000 sqft, and amazingly well insulated, can easily be heated/cooled to 72F by a 1.5kw minisplit running basically never.
Consider that your typical older long range model 3 had a 75 kWh battery in their first day, and one might typically charge it to 80%. So that 1kW, for one hour, is far more than a fraction of a percent of the practical battery capacity.
Mine doesn't have a heat pump, so I can definitely notice range decreases. Also consider that the battery likes to be at a good temperature, and that isn't going to be free if your car is parked outside for 8 hours. That changes range too
Your math is so far off, it isn't even on this planet anymore. In what world does an EV use more than 100kW? It's closer to 20kWh per 100km, so about 20kW on the highway probably. That would make your heater be 5%, not a fraction of a percent.
That's likely averaged out as 80kW when flooring it is only around 100hp. I know my Polestar hits a peak of around 300kW when you put your foot right down.
Now that you mentioned it, I looked up the specs for my car it does say the motor is rated at 160kW max. Indeed when the 80kW figure is displayed it refreshes every few seconds or so, so an average is likely.
