Coming from a Leaf, the cold alone isn't the biggest factor. Things like headwinds I find to be the biggest impact, followed by snow or crappy road conditions.
My ~25-30 degree temperature range has varied from just a 15% reduction of my normal battery, down to something like a 40% reduction, even without heater use.
My ~25-30 degree temperature range has varied from just a 15% reduction of my normal battery, down to something like a 40% reduction, even without heater use.