We have a 12 volt 50lt upright fitted in the camper.. Installed a fan under the evaporator (sealed computer fan). Fridge works well. Best when filled up. We also have a 50lt freezer. Just came back from seven weeks trip. Held enough meat and stuff for the two of us. (we topped up half way through our trip). At one stage we were way out of any town for over two weeks and didn't touch the can supply except for things like sliced beans, peas, baked beans to go with the bacon for breakfast. We ate well, steak, curries, rissoles, ect and came back with still half a freezer full.
So, I guess that equates to 100lt's...