Does anybody know how to determine how much gas is consumed (in a car) during idle with the A/C on?

Answer 1

That shouldn't be too hard to find out. Just fill the car completely full, run the car for an hour, then fill it up again. I'm guessing that your car will burn around a gallon or so per hour idling with the A/C on, depending of course on what you drive and how big the engine is.