Back in 2014 the advice that came with my Tesla was to use the heated seats/steering wheel to keep warm if range was a concern as they are run from a standard 12v battery whereas the heating/a-c affects range just like it does on a petrol car.
With M3s and MYs that have an air source heat pump and an octavalve HVAC management control the advice has evolved, now the advice is to set the temperature you want and the car will use hot air, heated seat and steering wheel to maintain a comfortable temperature. I have to say it works very well indeed. At the moment, with an ambient temperature of 5C I have the climate set at 18C and on short, less than 5 mile, trips the car is using 285 to 325wh/mile.
