Freezing is an excellent way to preserve many foods for a long period of time. As a result, freezers have become a staple in the modern household. Today, nearly all refrigerators have an integrated freezer compartment. In addition, stand-alone freezers, or deep freezers, are available when more storage space for frozen foods is desired. There are other differences between the two types.
Fridge freezers are constrained in size because they must fit into the overall dimensions of the refrigerator. Typical capacities for these freezers range from about 2 cubic feet on smaller refrigerators up to about 10 cubic feet on larger models.
Separate freezers have no such constraint, and capacities for household models typically range from 5 to 25 cubic feet. At the highest end of the scale, walk-in freezers of gigantic proportions are custom-manufactured for commercial and industrial applications.
Older-style refrigerators were equipped with a single temperature control unit. The temperature was set in the freezer and then an interior passage would allow a small amount of the freezer air to circulate down to the refrigerator compartment to keep it cold. The freezer temperature on these models usually could not be set below about 10 degrees, or food in the refrigerator section would start to freeze. In these early days the term "deep freezer" was used to describe a separate freezer that could be set at 0 degrees or lower, allowing the frozen food to be kept for a much longer time.
Today, all but the lowest-end refrigerator models have separate cooling control units for the freezer and the refrigerator compartment. That means the freezer compartment can be kept at the recommended temperature of 0 degrees or less, regardless of the temperature in the refrigerator section. Stand-alone freezers no longer have an advantage in this regard.
Stand-alone freezer models tend to be more energy-efficient than refrigerator-freezers, simply because they are not opened as often. Every time a freezer is opened, some of the cold air will escape, so frequent opening will drive up energy use. Chest-style stand-alone freezers have an additional advantage, since having the door on top of the unit means that much less cold air spills out when the door is opened.
It is important that the size of any freezer matches needs, since energy consumption is proportional to a unit's size. A freezer that normally is only partially full will needlessly consume energy to keep the empty part of the freezer cold. Regardless of freezer type, choosing Energy Star-certified appliances will insure the best energy efficiency.
All but the lowest-end refrigerators have self-defrosting freezers. Stand-alone upright and chest freezers are available in manual- or self-defrosting models; price usually dictates whether a freezer has the self-defrosting feature. If you live in a humid climate, or if you will be opening a stand-alone freezer door frequently, the extra expense of a self-defrosting model may be justified. For manual-defrost freezers, a chest freezer will require less frequent defrosting than an upright model.