Don't forget you can precondition your car before you leave while it's still plugged in. If I know I"m leaving at a certain time in the morning I set my desired cabin temp and trigger the Schedule to have the vehicle preconditioned for that departure time and its nice and toasty when I get in. I no longer need any more heat other than maybe the seat heater to maintain comfort. AFAIK it does all this using the power from your wall charger.