It is important to remember that an EV will have less range in the winter. How much less depends on many factors including outside temperature, use of heat, blower, whether the car is parked inside or out, and of course how you drive. Generally if you need to use the heater in your car you can expect at least a 30% drop in range. And this is assuming you do not get stuck in traffic.
Things you can do to extend your range include: pre-heat your vehicle before use; use heated seats for warmth; keep your cabin temperature set at 18 Celsius; minimize highway use; switch off the heater when stopped in traffic; and always remember to drive gently.
I can't speak for all cars or models, but can tell you that the smart fortwo ED I drive always underestimates and over delivers range. Just today, my car reported a range of 102 km when I started my trip. In summer that number would be 135 km. After driving with the heat on for 28 km, my car was still reporting 101 km left in range. So as you can see, the range indicator is giving me the worst case scenario and is adjusting as I go.
Just as point of reference, I do park inside a garage and leave my car connected to a phase 2 wall charger. Also on very cold days, I preheat my car before leaving. Feel free to contact me if you would like to know more.