I see what you're getting at, but not sure that's a direct comparison. Our fridge/freezer is about 150 litres (don't know what that is in cubic feet) but you're not trying to cool the van down to the same temperatures as the fridge (5C) or minus ?C for the freezer, just reducing the temperature 2 or 3 degrees can make a big perceived difference in the comfort factor - which is what we are doing at home right now. Reducing our bedroom temperature from 30C down to 27C makes it feel a lot more comfortable, strange though that may seem!It could be done but I suspect the gas consumption would be a tad eye-watering! Your gas powered fridge cools a cubic foot or two of well insulated volume. Now scale that up for the size of a MH. A non-starter I fear.