On my MH, when the generator is running, the power is switched through my inverter through a transfer switch and passes through the 120 volt generator power. When the generator is off (and no shore power), my inverter picks up the load and inverts MSW (modified Sine Wave) (Xantrex, Freedom 458, 2000 Watt) power to the outlets connected to it. My electric heater is 1500 watts and would drain my 4 golf cart batteries in a few hours if I used it with no generator or shore power. I use only the gas furnace when boondocking.
06 Hurricane 34FT WH W20 Chassis 8.1L 120K, Steersafe, Koni Shocks, DIY Trac Bar, Tri-Metric 2025RV Battery Monitor, 4-6V Batteries, Scan Gauge 2, Crossfires, 735W Solar Morningstar MPPT-60, KVH R5 In-Motion Sat, XM Radio, 07 Chevy Malibu Maxx Toad, Falcon 2, Brake Buddy, Escapee