How do you figure that increased demand for amps places an increased load on the engine??? The alternator is not like the a/c where it is engaged by a clutch. A 100 amp alternator has the capabiltiy of making 100 amps only, but does not mean that it will do so unless demanded. You do not place any more strain on the motor if you want 20 amps or 100 amps. The alternator spins freely and the load to the engine never changes. The wound wire that rotates past the magnets induces a current that produces power for your car. Let me know otherwise if you think I am wrong.