[Oldsguy]

Actually, clutch operated fans are not in continual motion as mentioned earlier so there is not a continual loss. The alternator is always being driven by the engine whether there is a demand for energy upon it or not so the argument about continual power loss could be made against the electrically driven fans as well. I am not making that statement just suggesting there is a possibility. I read a thread at ROP about this subject and someone claimed that when his electric fans kicked in during night when the headlights were on that it put such a load on the alternator it dimmed the headlights. Truthfully, I doubted it but can't dispute it, he was there. I think the amount of parasitic power loss from either source (mechanical or electric) is negligable (and un-avoidable) unless we are talking about a vehicle where you are trying to preserve every ounce of energy to make the vehicle go as the case would be in a drag car or in a high mileage competition at MIT.