Unfortunately, it doesn't warm up the car even as a joke, no matter how long you leave it....
It is only for defogging the glass and that only where the small airflow hits.
To understand, the air it produces can be felt at five centimeters without any exaggeration.
I'm saying this for anyone who expects it to blow air like, for example, a hairdryer, even one of the worst quality.....

It gives a little warmth... emphasis on the LITTLE... If the fan wasn't DEAD, maybe it would be worth something.... I will probably send it back... I didn't have any problems with connecting it to the car, but the fan is still VERY SLOW even in a simple breeze... In short, wasted money.... That's it...

The heat it produces is not sufficient to warm up the car space or to break the cold, and in terms of performance compared to the current it draws, it is high, about 15 amps, so its performance is very low, resulting in the battery struggling. The test was done with 12 volts and 55 amps, the voltage dropped to 10 volts with the car in motion.

It immediately produces heat, but not enough to warm up the driver. However, it breaks the cold inside the car. I have been using it continuously for half an hour and it had no problem. Time will tell. Anyway, if you put your hand in front of the outlet, it warms it up. It's worth the 20€ it cost.