Comfort and warmth
Fan heaters are a cheap alternative to expensive parking heaters, especially in the winter. They have a 12V connection and can be connected directly to the cigarette lighter. A timer can be used to set the fan heater to the desired time the night before. In the morning, even without auxiliary heating, you can enjoy a warm car with windows that have already been cleared of ice.
Incidentally, a fan heater also provides a clear view of fogged windows.
Since a fan heater in the car is powered by from the car battery and causes more stress in freezing temperatures. Therefore, you should not run the fan for more than 10 minutes otherwise it can happen that the car does not start afterwards.