We often wonder just how colder weather affects EV performance. Thusfar, I havenotheard any manufacturer of EVs 'get honest' with us about it.
Here in an article that seems to be credited to Kia..is an attempt. They say that in +20F degrees, a full charge is 40% low. ..And we who live in colder climes, also know that the power available drops exponentially for as the thermometer goes lower.
Personally, I suspect that at -20F, we should be surprised if it were 10% of normal power available..
Not only would your mileage drop, but that 10% would be just as costly to recharge as the full charge in mild weather.
Then if you desire some heat at -20F .... there goes more of your meagre charge level.
IMO...an EV can be nothing better than a "fair weather friend' at best..
https://www.cars.com/articles/how-well-do-electric-cars-work-in-cold-weather-459914/