FYI, you can force the engine to start and put some charge in your battery.
I tried an exparament, and ran my battery down to 0 miles. I then switched to mountain mode, and the engine started. It will only run for 15 minutes, use .38 gallon of fuel, and that puts 15 miles of range into the battery.
So never worry, as long as you have gas in the tank, you can generate all the power you need. I have used an inverter on mine to run 120 volt appliances. As long as the car is switched on the 12 volt battery is kept charged by the HV battery, and once the HV battery is drained, the generator will cycle on and off to keep the HV battery at min level of charge. If mountain mode is selected, the syatem will keep 40% reserve in the HV battery, which is 15 miles, or 25KM. I ran a 1000 watt inverter connected directly to the 12v battery, and ran a microwave oven no problem.