Having wired up a couple travel trailers and a boat (and, incidentally, being an EE who can theoretically run those calcs), I agree with the parent: It would be

Having wired up a couple travel trailers and a boat (and, incidentally, being an EE who can theoretically run those calcs), I agree with the parent: It would be better if the industry switched to 120V/220V AC for more parts, and away from 12V. The problem is that the ampacity in a 12V DC light circuit is 10x that of an equivalent-power 120V AC system. And worse yet, power dissipation in a resistive element is equal to I^2 R, so you're heating the wiring harness with power losses are 100x worse than in a 120V system and almost 200x worse than a 220V system. So you have to oversize the wires to reduce R, which adds weight and cost. And if you drop 2V to line losses in your 12V system, your device is seeing 83% of the nominal voltage, while if you drop 2V in a 120V system (you won't, because Ohm says voltage drop is equal to IR, and I is 1/10th that of a 12V system), but still, you're 98% nominal. They're running 12V because that's the voltage of a classic 6-cell lead-acid battery, and you probably didn't want 220V in your Model T, even with felted asbestos insulation, but I'd be confident enough to lick a modern XLPE wire carrying 220V. A century of using those lead acid batteries (and worse, 3-cell 6V systems...can't endorse converting your classic car to 12V enough...) created now-entrenched economies of scale for lamps, and switches, and pumps, and radios, and fans, and most of the other things you need in a boat or camper. The only advantage of using those 12V parts is that their manufacturers put a little more effort into making them efficient. No one (sadly) will notice or care if the AC-DC converter that runs the clock on your stove burns 5W at idle even though your wall clock can run on one AA battery for years, but they will notice and care if their camper battery is dead after leaving it parked for a couple weeks. Today, I recommend using LiFePO4 batteries in whatever series cell arrangement gets you the required watt hours, regardless of that output voltage. Then run a modern, high-efficiency (high-frequency) digital inverter to bump the voltage up to whatever your local AC grid runs at. You can go 220V AC in the US if you really want more efficiency and smaller wires, and are willing to deal with the hassle of finding the right lightbulbs and international power cords and so on.