Dan Fink has a good discussion on Choosing Your Off-Grid Refrigerator in HomePower Issue #176, November / December 2016. He describes the specialty refrigerators before he gets to the “conventional fridges.” The conventional refrigerators are getting to be quite energy efficient and the economies of scale can make them rather cost effective. Also note the comments about chest type freezers. These can also be had rather inexpensively but may need an external thermostat for refrigerator use. Also note the Colorado commenter who described his need to remove perishables from the freezer in the winter. That sort of problem could also be addresses by a separate freezer.
Advances in solar systems and batteries put ‘conventional refrigerators’ as a distinct possible option for RV’s. They don’t suffer altitude problems like many RV propane refrigerators do, they will chill down much faster, and can offer other advantages. The energy needs don’t seem to be influenced by size much. Big or little, a standard fridge seems to need about a kiloWatt hour per day of energy. That means a minimum base system of 2 lead acid batteries and 200 watts solar.
Dan gets into a lot of the issues and considerations on this topic. That helps to understand just what is involved and what to consider.