When the power was out over the summer I used a 1500W inverter and used my tractor to to power the inverter. (140A alternator on the tractor)
At idle, the big issue became cooling the alternator, as its built in fan was not drawing enough air for the output. This was only pulling ~400w (fridge, freezer, light and radio)
Even with a 140A alternator running fill tilt, it would only be able to sustain about 11 amps at 120V with a decent inverter (80% efficent) before you will start to lose battery voltage.
That said, it works in a pinch, but I would rather use the 80KW genset in the garage. Also reasonably sure I don not need to worry about someone trying steal the genset if I leave the key in it.