I agree with others who say you preheat the car using the phone app and try to time the charging so it ends shortly before you will leave. Don't "start" the car.
And if your car is plugged in, the preheating will come from the charging circuit, not the battery. But if you want to be comfortable and do not need absolute maximum range, go ahead and preheat even if you are not plugged in.
BTW, I am nearby, in Dedham, and my experience is that you only need a few minutes of preheating on a chilly day, but you might need the full half hour only on the coldest winter days.
One other note: The heating system will turn on as you left it. So you might want to think about how to set the controls (auto vs manual, fan speed, recirc, etc) to get the most benefit from your preheating. The seat heaters cannot be actuated remotely, though, nor can the Defrost mode or heated steering wheel or other features. (Although the Defrost mode cannot be turned on, you can set the air flow to include the windshield.)