The older Tesla's do lose up to 30% range in the cold, but all the currently sold Teslas have heat pumps which largely fixed that problem. It's true that you won't get your rated range unless you're driving on the level and not going faster than 55, but you'll get more than enough range to get between Superchargers on road trips or to putter around town all day. If you want to putter around town all day and then leave for a road trip, you better super charge in between.