altenator power draw

[sfnz]

can anyone enlighten me on just how much HP/ energy is required to run an altenator, more specifically if for instance it is fixed prop/ shaft driven and if say altenator is 35 amp output would it require more HP/ energy if it were 24v as opposed to 12v, naturally not expecting full altenator output but anything over 4 or 5 amps is a big plus. Back in the 80's did a tour through the southern ocean Auckland >>Punta Arenas etc etc on a steel boat with a shaft altenator and that kept up with things pretty well electrically

[smac999]

1 hp = 746 watts, (+ inefficiencies ) voltage doesn't matter only total power.

so yes a 24v 35a alt would take twice the power as a 12v 35a alt. or the same as a 12v 70a alt

about 1hp