As you probably know, there's a 12 volt battery in these cars. That battery is automatically recharged by the big 100kWh main battery.
Some years back, I bought a 12 volt, 2000W inverter and connected it to this 12 volt battery in the Tesla, ran a couple of extension cords, and powered our refrigerator, extra freezer, and a number of other things with it for many hours. The main battery percentage in the car showed an appropriate drop. This actually wasn't during an outage, it was contingency testing. We already have a natural gas, 3600 watt generator that connects to one of our panels and use that during (unfortunately frequent) outages.
In my 2017, it's a bit of work to get to that battery, but it's quite doable and seemingly quite safe. The obvious, very rough/estimated/simplistic math is the 100kWh main battery divided by 2kW is about 50 hours. Different factors would push that number up and down of course.