It depends on your individual usage. Do you plan on showering in the trailer every day? Do you plan on using microwaves, tvs, electric heaters, toasters, hair dryers, etc.? Do you have a residential fridge or a 2-way fridge? Do you want to use a generator? What type battery? How many?
For me on my own, a 4-day trip will use no more than 20 gallons fresh water (including drinking, washing, cooking, cleanup, etc.), 10 gallons black tank, 10 gallons grey tank, and will barely touch the battery power or propane. I could reduce my water usage in half if needed. No generator or solar used.