OK, first your RV has a furnace and a water heater.
the furnace uses propane to heat, not electricity. It uses 12vDC battery power to run the fan and lite the burner.
running the generator only recharges the battery, since the furnace fan is the biggest consumer of battery power.
there's no electric heat in RV's, unless you get separate heaters, like a ceramic one.
many of us use them to supplement the propane furnace if you have shore power.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC