I'm running a xantrex prowatt 2000 with six GC2. I just tried a 1500 watts hair dryer. On high it was pulling 113 amps and took the volt meter down to 12.1. I switched it to low power and it pulled 45 amps then went back to high setting and it dropped to 11.9. After shutting it off the batteries come back to 12.5 and would probably hit 12.6 in a little while so of course it's just sag from such a heavy load but it is a very large draw.
DW said she always uses low setting
Edit: it's now been sitting for a little while the furnace is kicked on a couple times and it settled back at 12.6.
You need enough battery that the voltage doesn't sag so low that the inverter alarm kicks off