We camp in winter in northern WI.
Fully winterize the RV, blow out all lines, and rv antifreeze to traps, etc.
We only use the toilet in winter and dump rv antifreeze to flush.
We don't use fridge, its cold enough outside for whatever needs to be cold.
We are plugged in at our seasonal site for furnace electricity.
We have the standard 30lbs propane tanks plus we added a 100lbs propane tank to the regulator.
The campground we are at has a shower in the back of the bar/grill that is available to us in winter.
Obviously, when not in bed I go number 1 outside.
We have about 6-7 families that camp all winter long at the campground.
Heck, one of the guys even brought up a snowblower to leave there to clean up driveways and fire pit areas.