I found some data on Tesla model S heaters and HVAC power requirements:

https://www.teslarati.com/energy-saving-tips-tesla-subzero-weather-using-seat-heaters/Some interesting parts (the article is longer):

At one point, Kman turns on the heater to ‘HI’ (82F) – commonly used by owners when first entering a frigid car – and measures a staggering 16.8A, 6.4kW of power consumed, or 18+ miles of range lost per hour. Though running the heater at HI for an hour is an unlikely scenario, especially considering the fact that the cabin temperature quickly reached 108 degrees Fahrenheit (42C) within a short amount of time, Kman brings to light that quickly warming up a vehicle using the heater could have significant and detrimental effects on range.

Tesla Subzero Weather Package + HVAC Energy Consumption

Energy consumption has been broken down by feature. Total energy consumption can be added together based on the number of features that are enabled.

Assuming a consumption of 333Wh/mile, we can compute the approximate range loss at miles per hour (mph) as a result of having these heating features on.

Baseline (vehicle at rest but powered up): 247 Wh = .74 mph

Defroster (rear window & side mirror heaters): 285 Wh = .86 mph

Steering Wheel Heater: 95 Wh = .29 mph

Heated Wipers & Nozzles: 95Wh = .29 mph

1 Seat Heater: 57 Wh = .17 mph

2 Seat Heaters: 133 Wh = .40 mph

3 Seat Heaters: 171 Wh = .51 mph

4 Seat Heaters: 209 Wh = .63 mph

5 Seat Heaters: 247 Wh = .74 mph

HVAC at ‘HI’ or 82F (28C): 6.4 kWh = ~18-20 mph

HVAC at 74F (23C): 342 Wh = 1.03 mph

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Does that mean that the HVAC system uses 6.4 kW to get a 28 degree C difference, but only 342 W to get a 23 degree C difference? Isn't that like too much of a difference?

Also, 6.4 kW seems like a lot to me, considering that one room air conditioner here (with a quite decent size) has a maximum power requirement of 3.2 kW. But i don't know anything about car HVAC systems, maybe they need to be that large for some reason?