I have the Yamaha instead of Honda, and when they're parallel they run full bore. The 13,500 AC will not start on eco. My 5 gallon Evinrude tank drains fast running both generators, last dry camp I achieved about 12 hours before the tank was nearly empty... I stopped before it started sucking air. EDIT: I should add, when I'm running my generators, they are working hard - running the 125 amp charger on my inverter, as well as the AC unit and dehumidifier.
It's kind of sad how inefficient these little generators are - the 6 horse power motor produces 4.4 kW of energy at peak output, but mechanical and electronic losses from converting that twist into A/C power yields only 1.6 kW of peak electrical output (discounting surge)... 1.6 / 4.4 is only 36% efficient - just sad.