alternator draw

Yes there is a substantial price to an alternator. People usually do
not point this out when recommending mega-alternators, but 750 watts
is equal to 1 horsepower. Figure it is charging at 13+ volts and
there is 10 or 20 percent inefficiency, heat generation, pulley drag,
etc, each 40 amps costs about 1 HP. Not such a big deal on larger
engines, but a significant proportion on smaller auxiliaries.
John Churchill