My toy hauler has a 5500 watt Onan generator. In non-winter weather, the generator is primarily used to run the microwave. I rarely need air conditioning unless I'm in Moab in July. Otherwise, the solar does a good job of keeping the batteries charged. I use an inverter to make coffee and charge my laptop.
In winter, I use too much juice to run the furnace and the generator needs to run for a while to bring the batteries up to a full SOC.
I've been looking at replacing the current trailer and have considered leaving out the generator. If I put in enough solar (1200 watts) and battery (LiFePO4), I can get by without an on-board generator. The generator compartment could be used to house the solar components and batteries. I'll likely have a small inverter/generator just in case.