I also have a Honda 6500, electric start, auto throttle. Power went out Friday night, back on Sunday night. I went through about 12 gallons of fuel. The only thing that has the genny throwing her shoulder into it, is when the well pump kicks on. Initial load bounces the gen tran meters, otherwise she just hums along at a relatively quiet drone.
I don't run it over night, this time of year. No point in it. there is really nothing that needs power this time of year. Get the house nice and warm before bedtime, Up at 5:30 AM, fire up the genny, fill the wood stove and let the circulator pumps go back to work.
If it was January, I would run the genny all night. -20 F is too much differential to trust the plumbing to.
The whole experience this weekend had me rethink the PTO vs stand alone. I have two tractors, so committing one to that duty is not the issue. The honda is a 2 cylinder machine that is pretty miserly with fuel. My smallest tractor is a 4 cylinder diesel (Kubota 3710). The genny has auto throttle, the tractor, does not. On the whole scheme of things, I would rather be running the stand alone genny unit.
It takes less than 5 minutes to have it up and running, and my bride can do it. A pto unit would require going to the barn to get tractor, rigging the genny, moving the unit to the gentran outlet and then the 5 minute set up.
Plus it involves running my tractor at sufficient rpm's to deal with the peak load cycles. I come to the conclusion that having the RIGHT tool for the job is almost always better than over kill. A PTO genny is over kill for me, and now I am certain of it.