Amperage & Power Data for Gauges and APU

HiWould anyone have the actual data specs and power requirements regarding the gauges used on a real 747 and also about the APU on what its max amp output would be at 1,450 horsepower. It is well understood that the APU can put out a lot of power but at same token it can only give so many amps as well. When I see the amp ratings on the CFG it is twice of what that APU can put out. Keep in mind that APU is only a 1,450 horsepower unit.Also would anyone know the precise bus ties each is linked up. We have 4 bus ties with 4 engine generators. So it would seem to me not everything runs off the main bus itself. Example nav lights, bus tie or hot line or battery line, max ampsand so onI know that some of the gauges only work from engine generators or APU and some is operated on the by-pass hot line, and some is off the battery. Yes the APU can start on its own without outside power but this is only if the service is not available at such airport. A lot of times they just let the APU run all night powering the aircraft itself. It only uses 50 gallons of jet fuel an hour and a lot more less during the night time. So for 6 hours of run it will only use up max 300 gallons and minimum of 150 gallons.I cannot seem to fathom that when I see on the CFG all the power is off of the main bus except for avionics. Cannot be true.Something is wrong there. This is why I am asking for the real information if anyone has it and if they can be so kind enough to post it for me here.