I have been bothered by the range lost in cold weather. I regulary make a trip that is 150 km and in the summer it only uses ca. 80% of the battery. In the winter, I always have to use Range+ and when the temperature comes down to zero, I will have stop for a 30m charge, ie. the trip is using 130-140% of the "normal" batterycapacity.
I tried some experimenting, and found out, as some of you also have, that the heater is using a lot of power. If I ran the trip without the heater on, it was possible to do the whole trip with Range+, that means that the heater is using almost 30% of the battery capacity, and that is a to much.
After som very cold trips, and a lot of hot tea, I decided to fix the problem myself. The solution was simple, I went to the local plumber shop and bougt three lengts of pipe insulation, I think it was 12mm, 24mm and 32mm. It was last summer, so I can't remember it exactly, but you can easily measure it on the pipes and hoses. Then I just insulated the hoses and zip-tied. You can feel which ones to insulate by feeling if they are warm after a short trip with the heater on.
The result is fantastic. I am now able to make the trip in the winter in one go, and still have a decent heat in the car. It's not like Ibiza heat, but I makes it comfortable to drive in normal winter clothes. The trips now uses ca. 110% of capacity with zero degrees C and even less at 8C that most winter days are here.
I have some pictures to show the end result. Be sure to get the 2 hoses furthest back in the middle properly insulated the whole way back. I did it by putting the insulation on the hose, and sliding it on the hos until it stuck. You could probably get under the car and do it better, but I don't have a lift.