Here is an often-shared article on 12v systems. Maybe itíll help:
Basically, your battery will run the furnace blower, water heater (maybe), lights, and possibly the fridge (depending on a few factors- itís either all 120v or propane+electric). There are 12v TVs - theyíre less common but sometimes come in motorhomes.
Otherwise, if itís a regular household outlet, itís 120v. You either need shore power, generator, or an inverter.
Just remember- your battery power is typically fairly limited. You canít go hog wild without running it down at night. Run it down too far and you can damage the battery(ies).