[8fingerlouie]

It depends A LOT on car, battery make, and temperature.

For temperatures above -10C (14F), a car with heat pump will typically have a range drop of 20-30%, where a car without heat pump will have a somewhat higher range drop, but when temperatures go below that, the heat pump becomes increasingly less efficient.

Some cars will back a backup PTC heater, where others, like (recent) Tesla Model 3/Y/S will run a motor to generate "waste" heat.

Some cars will also scavenge waste heat from the battery, while others cannot.

Some personal experiences in -15C (5F) is that Tesla Model Y LR loses about 25% range, where a VW ID.4 Pro loses closer to 40% range, despite having a heat pump. Ranges are measured on the same stretch including city driving and highway driving.