Living in a region were you need to warm up car for 5 minutes to stop it being an unwelcoming block of ice, and experiencing frequent failures to get the starter running due to discharged battery due to cold, I always wondered how much cold affects battery performance and his much the heating costs in miles. Tesla's figures look unbelievably good, and I think they don't account for heating. In -20° you'd need at least 1-2 kWt heater to not freeze, so heating alone would take 5-10% of total energy consumption.