If your fridge has LED's on the front, is self igniting or has a simple switch to change modes, it needs 12VDC in order to function. Same with the more recent water heaters. The furnace fan is 12VDC too!
You need 12VDC power for practically everything nowadays. My old trailer (1983 build) had all manual appliances. But the trade-off to get rid of the wasteful standing pilots has been reliance on the battery. Throw in the CO & gas leak detector and you've got to keep that battery above 75% charged the whole time you are out in the field.
I've had to pack a 2kw genset to charge the battery on my new trailer. 2-3 hours generator run per day is adequate.
TT 2015 19RD "TheJayco"
TV 2003 F-350 "Montblanc" - Housebroken chore truck
Sitting in The Cheap Seats.
And proud of it!