You may have heard of this trick before. You can save energy on the operation of your freezer (or refrigerator) if it's only partly filled by freezing (or cooling) bottles of water. It takes energy initially to get the water down to temperature, but once it's down there, it will hold its temperature a lot better than air. Water is about 800 times denser than a comparable volume of air, and water has a specific heat about four times that of air. So, you're looking at over 3000 times the heat necessary to heat up a bottle of water than to heat up the same volume of air.
Essentially, the cold or frozen water is like “cold ballast” that really resists changes in temperature, especially when you open the door.
A side benefit is that you can reuse (rather than throw away or even recycle) a few plastic bottles, giving them a little bit more of a useful life.
That is a great tip that I'm going to be trying out. Thanks for the insight.
Interesting tip…I've never heard this one before. Any idea what effect this really has on the energy consumption of a refrigerator? What kind of savings does this equate to?