Ok thank you all for the suggestions. Since not one of you attempted to answer my original question which I repeated twice (see posts #10, #6, and #1) I will look somewhere else for the answer.
I'm looking for a well thoughtout, perhaps of mathematical origin, of whether 300watts of additional electrical load on the alternator uses more or less energy than the ac compressor. If someone knows about air conditioners and can provide a solution to this question, please PM me. In the mean time, I will continue my googling.
