There is nothing worse for energy efficiency than an empty or sparsely populated, refrigerator. When there is little thermal mass created inside to absorb and store the cold air, the cooling apparatus works overtime to maintain the desired temperature.
Here are a few tips for better empty fridge efficiency:
1. If your refrigerator is almost empty most of the time, fill up containers of water and store them inside your fridge. For an empty freezer, store some extra bags of ice. This will create more thermal mass inside your fridge and will give your fridge's coils a break. In a power outage, the extra bags of ice will also help to keep your food from going bad.
2. Downsize. If your refrigerator is always on the empty side, downsize to a smaller one. If you find that most of your refrigerator is used to store sodas, beer or other items that only need to be cold for a few hours before using, this is a good sign that you can downsize to a smaller fridge and keep the overstock in your pantry. The sodas and beer DO help to create thermal mass, however, if a smaller fridge is a sore subject.
3. Cook and eat at home more often. You will then have more food and more thermal mass in your fridge.