Like the others have said: It all depends on your need
I have minmal needs so 2 group 31 AGMs (Lifeline) and 200 watts of solar keeps me going. I don't watch TV or use the Microwave. In the summer if its really hot I will use my Honda 2000 to run the AC. All my lights are LED and at most I run a 200 watt inverter to charge my Laptop. The main camper drain is the fridge circuit board on the Fridge and in winter the furnace and when its really hot or cold out I cover the doors windows and vents with reflectix and foam and have fiberglass batts behind the external hatches to maximize my thermal insulation from the outside environment. I camp year round in all sorts of temps from near zero F up to above 115F.