Here is how its done? Remotely start your car. Having selected defrost and heat on hi the night before the window will start to defrost after a few minutes. I then through a pot of hot tap water on the window and the air intake just below the window . It gets plugged up with snow every few days if its been snowing.I then spray the window with the cars own windshield deicing fluid to get rid of the water so it wont re freeze. I have also used warmed up windshield deicing fluid instead of water. Its a bit more expensive if money is an issue. Some newer cars heat the windshield deice fluid. I have also used this method to deice my plane followed up with some good old xl 54. This is an approved method for aircraft. Aircraft deicing fluid is heated to 160 f and poured on in copious quantities. Ive never cracked a window and one of my cars has a stone chip. It has not gotten any bigger over the years. This particular car is almost 20 years old.