Does a Refrigerator Use More Energy When Full?

Please settle a debate for me. Does it take more energy to keep your freezer running when it is full of food or when it is empty? If you look at a slightly different question, I believe this hints at the answer. Let there be a boiling 5 gallon pot of water and a boiling 10,000 gallon swimming pool. Which takes more energy to continue to boil the swimming pool or the pot of water? (obviously the pot of water). I believe this is relevant to the freezer question.
- Scott Stalker (age 37)
Albany, NY, USA

Hi Scott,

When you first put the food in, it will have to work a bit harder to cool the food down. Once the food's temperature equals that of the thermostat, the freezer will require about the same amount of energy in either case.

If you boiled 5 gallons or 10,000 gallons continuously, you would lose most of the applied energy into the environment, so you would have to continuously add more heat. In contrast, your freezer is designed to leak very little heat into its surroundings, and the amount of leakage probably doesn't depend on how full your fridge is.

Other than leakage, heat can escape when you open the freezer door. If you keep your freezer full, then less air will escape each time you open the door, saving you a little money. However, a quick calculation using basic thermodynamics shows that this effect is small as long as you don't open the door many thousands of times per month.

If the cooling mechanism in your freezer was not inside a nice insulated box, but rather kept food cool in open air on your kitchen counter, then it would be analogous to the boiling water, and you would need more energy to keep more food cool.

David Schmid

(published on 03/14/2013)