Inverter question about 12v draw

smkettner wrote:
Loss will be 10% to 15% so 50 watt load is ~55 watts out of the battery.

55w / 12.4v = about 4.5 amp battery load.

This is probably a reasonable estimate of inverter loss on house size inverters. Smaller ones generally are somewhat more efficient so 6-7% loss might be a good number if using a small dedicated inverter. It also depends on what you're using the loss comparisons for. If you're comparing inverter on to inverter off, you need to also include the phantom loads that you'll pick up when you turn the inverter on. These are what the coach builder hard wires into the 110V system and doesn't tell you what they are and where you MAY be able to go to shut them off. In many cases, these can add up to another 10% loss when that big inverter is turned on.