Normal winter for battery power drive train. If you have 300km rated, it is realistically closer to 200km.
Resistive heating for the cabin and battery pack zaps your range. If you're solo commuting and want to maximize range. Lower the cabin temperatures to 16 to 18C (it will feel colder on a cold day/highway speeds) and have a blanket. This should bring you up to the 80%ish efficiency range. I don't think this is worth it unless you're OCD and want to maximize Wh/km. Be warm, comfortable, and enjoy the ride.
My commute is 120kms, during the summer I sometimes have 100%+ efficiency. Winter, its closer to 60% efficiency (21C cabin temp) and lower regen rates - thus more usage of the brakes. It only affects long road trips (more Supercharging and more often) or days where you're busy and running around town doing a lot of short trips. Charge to 90% and know where you can destination charge (if in an winter storm emergency, lower cabin temps to 16C and have a blanket ready).
You can expect your cost of electricity for the EV to double during the winter months. You're using more energy to heat the car/battery.
2018 Winter:
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2019:
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