Improving refrigerator efficiency

I live alone, and my kitchen has a typical refrigerator designed for a full household.   I am not one of those people who needs to keep a lot of food in the refrigerator, so it sits largely empty most of the time. One of the drawbacks of a lot of empty space in a refrigerator is that it becomes inefficient.   Every time you open the door all of that cold air falls out.  If your refrigerator is filled, there is less air to fall out, but more importantly there is more thermal mass storing the cold inside.  My solution to an increase the efficiency of my refrigerator is to store gallons of water in old milk containers.  This is a simple, easy solution that seems to reduce the run time of my refrigerator.  If you have empty space in your refrigerator, I suggest you save some milk containers and rinse them out thoroughly and store water in them, it's always handy to have some cold water around anyway.