The numbers I’ve seen quoted are in the neighborhood of 20-30 percent, but that’s only really for cold weather. Tesla batteries are actively cooled, so there shouldn’t be a significant performance decrease other than the power draw from the AC unit in the cabin.

Even if there were a 50% loss in efficiency the car should still be able to travel over 150 miles, the notion that the weather would drop the range to less than 80 miles is absurd.