Most new RV owners don’t realize that their rig runs on two completely separate electrical systems, and which system powers what device dramatically affects how long you can camp without hookups. Your RV has both 12-volt DC (battery) and 120-volt AC (shore power) systems, but many appliances can run on either depending on your power source.
Here’s where it gets tricky: when you’re plugged into shore power, your converter automatically runs 12V devices off the grid while simultaneously charging your batteries. But when you disconnect and go boondocking, suddenly your water pump, lights, furnace fan, and refrigerator control boards are all drawing directly from your battery bank. The refrigerator alone can consume 12V power even when running on propane because the control board, interior light, and ignition system still need electricity.
The biggest surprise for new owners is learning that their converter isn’t an inverter. A converter changes 120V shore power down to 12V for your lights and water pump. An inverter does the opposite — it changes 12V battery power into 120V household current for your microwave or TV. Many RVs come with a converter but no inverter, which means when you’re off-grid, you can’t run standard household appliances at all.
Before your first boondocking trip, identify which devices run on which system. Your water heater might run on propane, but its electronic ignition needs 12V. Your furnace burns propane for heat, but the fan that circulates warm air is a major 12V draw. Understanding this split helps you calculate realistic battery life and decide whether you need to add an inverter or more battery capacity.