A 20% drop in range is spot on, if it is in the teens where you are. Get used to it, and make sure your tires are at 38 psi minimum after sitting overnight.My 2020 Bolt in cold weather shows a maximum mileage after full charge ~ 200 miles considerably down from the usual ~ 250 miles during the summer. I keep the heat off and use the seat and wheel heaters to stay relatively comfortable. My usual use was to drive 150+ round trip per day. I have been tempted to buy the outboard equipment to look closer, but then think, I will take it to the dealer at my next wheel rotation for a check and to determine their skill level in dealing with any Bolt issues.