I just discovered something all over again. It’s a tidbit I was confident about already but in my preparations for Hurricane Sandy it became abundantly clear once more: A full freezer stays cold longer and conserves energy.
It’s pretty obvious to most people, but probably for the wrong reason. You see, most folks think a freezer is filled with cold air, and cold food, and other cold stuff. They feel as though if you open it, you’re letting the cold out. As though cold is a quantifiable substance. That’s one way of looking at it, but the more accurate perspective is that the contents of the freezer are missing the energy that’s present everywhere else. Cold is like darkness, which we all more intuitively recognize as the absence of light. And like darkness, you can’t “add cold” to something any more than you can “add dark” to a room.
So what does this have to do with a freezer? Well a freezer removes energy from things through a series of simple mechanical processes and dumps the heat from those things into the room around it. Once that work is done, the insulation in the freezer walls prevents that energy from making its way back into those objects. Lets use water ice as an example, since its a key part of this process. Water molecules are the wrecking balls of the chemical world in many ways, the one most relevant to this conversation being that they have a great deal of inertia. In other words, they’re hard to get moving, and when you do get them moving, they’re hard to slow down again. It’s an energy sponge.
Again, what does this have to do with keeping the freezer full? Well imagine that in order for your freezer’s temperature to rise, all of the ice in it had to melt first, and imagine you needed to put a stick of dynamite in your freezer to melt it. That’s an exaggeration, but it’s a relatively good way of comparing the amount of energy that gets added to your freezer when you open the door against the amount of energy it takes to thaw ice. That energy sponge (water) has to be full before your freezer will get any warmer!
So get to your kitchen and fill every ounce of empty space in your freezer with plastic bottles of water. Leave a little more than a third of each bottle empty and don’t screw the caps on too tight. Water expands by 35% when it becomes a solid so if you fill the bottles, they’ll just burst as they freeze.
Once it’s all frozen you should find that your food freezes faster and your fridge doesn’t work as hard or as often. You’ll also find that if the power goes out, you should be able to keep food frozen longer before spoilage. Hurray! Science!