What definition of "standby" are we using? To me standby means the unit has power, but the inverter is shut down, it's not running, it's in standby.
If that's the case, my Magnum doesn't even register 1 amp, which concurs with the datasheet, standby-searching < 8w.
However if standby means the inverter is powered up and active, but no AC appliances are turned on, the datasheet lists that as inverting-no load < 30w. I haven't made that measurement, as I have a bunch of AC appliances connected that have no on/off switch and I'm too lazy to unplug them all.