First thing you will need to do is figure out how much load you are going to run when the power goes out. I would assume refrigeration but what else will you want to power? Do you have electric only for cooking? In which case you will probably need something bigger than most caravaners carry around. Once you work out your total load you will then need to add some extra capacity for start up load, a fridge can pull triple or more its running power as the compressor kicks in. If noise is a problem you can build a sound deadened enclosure for the generator but make sure the exhaust is vented outside.
