I have made one of this type of heater that fits into your car cup holder and plugs into your power acc. port. It gets up to 1000 degrees f in a matter of 30 seconds. You can use it as a stand alone heater or to heat the car up in half the time. The trick is to calculate the watts, amps and current. My heater is a approx. 100 watt and pulls 7.5 to 8 amps. and puts out 1000 degrees. This is a radiant heater with no fan and heats up the objects in the car and not the whole car. It took me a while to figure out how not to melt my cup holder but is now very safe. I have been using the heater for three years now with no problems because there are no moving parts to go bad. It costs about $50.00 to make.