If you didn't already know, I live in a 26 foot foot travel trailer.
These things have a built in converter that turns 110 volts into 12 volts to run all the lights.
It originally had a refrigerator that would run on 110 volts, 12 volts or propane. Not unusual for one this vintage, it was belly up.
There is a propane furnace that runs off 12 volts, it is belly up too. I have torn it out twice,( no small feat) to try and fix it and finally threw in the towel when it blew the sight glass for the pilot light off one time too many when it backfired and it shattered on the wall clear across the trailer,mere inches from my face as I knelt down to observe what the hell was going on with it. Right now I just use little space heaters but I have the Grand daddy of propane heaters out in the shed, I have to vent it to the outside yet. About two minutes and you have to shut it off, it will go from 35 degrees to ninety that fast.
I don't mess around when it comes to being cold. I have already built a stove of sorts that it will fit inside, I just have to plumb the exhaust.
Anyway, twelve volt systems can do a lot of things that your normal 110 volt systems can.
Think of the fanciest car you possibly can, Heated seats, power windows, mirrors, seats, killer stereo, GPS system, DVD players with video monitors for the passengers to watch,digital programmable dual heating, just think about all the fancy things that cars have these days and remember one thing, they all run on 12 volts.
The kid in this video is obviously a Geek but he can show you a thing or two.
I was playing with 12 volt toys before I knew what a volt was.
Back in the day, little toy train sets and slot car sets all had 110 to 12 volt transformers.