Okay Hondo, to directly answer your question, "Nothing".
That is assuming that there is an inverter as the previous owner told you there was.
So now here is the question others have asked;
What is it you want to power with 120 VAC and what is the draw in amps. If it is for several purposes, what would be the maximum combined draw?
What is the capacity of the "Very Large Capacity" inverter you have now?
What is the available ampacity of the 145 amp alternator. 145 amps less the maximum charging draw for the batteries, ignition system and other accessories like radio, frige.
Once you learn that, you can figure the net amps avail to use in the inverter. Figure that you're going to get at best 80% efficientcy from the inverter or if there are 70 amps available, you'll be able to install a single inverter rated at 840 watts or roughly 7 amps of 120 VAC power.
A good PSW inverter rated at 900 to 1000 watts will cost you between $400 and $600 dollars. I couldn't find any 850 watt inverters in my catalogs. And figure another $50 to $100 for materials to connect the inverter to your 120 VAC system. That's a lot of money to get 7 amps per hour. Your genny will probably provide 25 watts per hour for about $1.85 an hour.
If you're figuring low hours on the genny will add to the resale value, you may be mistaken. 60 or seventy hours per year isn't much when you need to exercise it 12 hours a year minimum. I don't know what the average number of days an RV is driven per day but I would guess not many.
In my opinion your not going to gain anything installing a really big inverter.
"I travel not to go anywhere, but to go. I travel for travel's sake. The great affair is to go". R. L. Stevenson
David Bishop
2002 Winnebago Adventurer 32V
2009 GMC Canyon
Roadmaster 5000
BrakeBuddy Classic II
