The other day I decided to drive with the heat on for my entire commute to work. It was in the 50s so I set the fan to 1 and turned on the heat to 2 clicks. I also had the head lights on as it was foggy. Yes my range dropped, about 10%, after the 20 miles I had 90 left, I'm usually around 100 left. My % was at 83% while I'm normally at 88% to 90%.
On my return I had the wipers and lights on as it was raining, no heat, plus drove a little harder. The MINI E is fun in the rain. When all was said and done I did around 41 miles that day and had 63 miles left on the range indicator and 62% on the capacity, about 1% for 1 mile. Since I'm on the 110 I will fall behind during the week, with the wall box installed it won't be an issue for my commute, now if I want to take a 100 mile biz trip again that might be a real challenge.