So maybe it's not that much more efficient but 6 tenths of an amp is nothing to snub your nose at. The 400 watt inverter ran the TV using only 5.2 amp hours per hour of run time and was a mere 25% inefficient. Again this is a far cry from the 10% claimed by most manufacturers, and believed by boaters.
This certainly was not a very scientific experiment but rather a real world experiment designed to show what one item, a TV, designed to run on both 120 volts AC and 12 volts DC, will do run both ways.
It is clear to me that if you have the option to buy a device that will run on 12 volts DC vs. 120 volts AC, you should buy it. Inverting power from 12 volts DC to 120 volts AC, then back to DC again is a terribly inefficient way to power devices off your boats house bank of batteries..