New user and it's warming up! If I turn on the AC fully the range drops by 15 miles, is that 15 miles on the current battery power, i.e. is that the top limit for the journey until I get a new charge, or does the range drop further the longer I have it on?
the 15 mile range drop is the car assuming you will drive with the current settings until the battery empties.
given you have ac on full the range could go up a bit if outside temperature drops - ie ac doesn't have to work so hard - given its on full increasing external temp won't have an impact on ac use but could also increase range just because of increased battery efficiency with temperature.
If you have ac on auto then it will adjust as much as it can.
I have found that in reality the A/C is not actually that hungry. In fact, on a 200+ mile trip last week in the heat it probably made a difference of less than 10 miles regardless of what the dashboard range estimate said. It is the heating that makes the biggest difference.