not many studies done on alternator loads effect on fuel economy. i attended a class on gm's new strategy to turn off the alternator under cruising conditions and the results are nil on an individual basis as far as fuel economy goes. tenths of a gallon in the name, but on a national scale equals alot of savings. which means alternator load does very little to fuel economy. the extra load a hho generator puts on the alternator does not lower fuel economy enough to negate the generator but may cause the alternator to fail prematurely.