John M. Broder for The New York Times:

Tesla’s chief technology officer, J B Straubel, acknowledged that the two East Coast charging stations were at the mileage limit of the Model S’s real-world range. Making matters worse, cold weather inflicts about a 10 percent range penalty, he said, and running the heater draws yet more energy. He added that some range-related software problems still needed to be sorted out.

I think that 10% figure is extremely low. Tesla uses lithium ion batteries similar to those found in the Volt. I’ve found that I lose nearly 25% of my range (~43 mpc to ~32 mpc) when the temperature is in the 30s. That seems more in line with what John Broder experienced in the test.