Thanks for your contributions Freebeard and Piotrsko. So I see that my calculation seems to give something between the two examples that you gave

As you know, the motor consumption will be very variable depending on the instantaneous speed of the car. In my case, the usage that I have in mind would be a car running less than 100 miles per day, with a average speed of 15 to 20 MPH. My idea is that, thanks to this low speed, I should not have an heavy consumption (confer the calculation I put in my previous post), and also I hope to be able to drive 100 miles with no more than 15 KWH... But I don't know if this goal can really be reached...

Anyway, what about the plans and schematics of the Paul&Sabrina's AC Controler ? Do you know where I could find out these ressources ?