I'd imagine our '08 knight is very similar to your Neptune.
We also do not have inverter outlets in the slide that contains the bed, a non inverter outlet on each side of the bed.
Opposite, in the slide that contains the TV, those are inverter outlets.
Our inverter is a magnum me2012, 2000 watts. It is located in the compartment directly below the head of the bed, right behind the batteries. It has 2 pushbutton 15 amp breakers on it and powers 2 circuits of outlets, almost everything, but not the bed slide. I'm not sure of the routing of these wires, other than that they do not go anywhere near the main breaker panel, my main panel is in the rear closet.
The wires from the 2 outlets in the bed slide route to the rear, into the box in the closet that contains the water heater, house 12v fuse panel, and main A/C breakers.
I once tried isolating which circuit the bed slide outlets are on, and what else is on that circuit, but it was a long time ago and I gave it up.
The only time our family uses either of those 2 outlets is DW charging her iPhone while she sleeps. She's been convinced to plug it in across the room.
If we needed a CPAC or something, I would find a way to power those outlets via the inverter. It wouldn't be that hard to do.
Sorry for the length of this, hopefully knight and Neptune are close enough that the info will be helpful to the OP.
