The California Energy Commission reports that bottom freezer refrigerators are more energy efficient than traditional top-freezer models but doesn't say why. Other sources, including the federal EnergyStar program, maintain that refrigerators with freezers on top have the energy edge.
Energy Star compared top-mount, bottom-mount and side-mount freezer models, all without through-the-door ice dispensers in 2008, information that it updated in 2010. It noted that top-mount models on average used 472 kilowatt hours of electricity per year, bottom-mount models used 551 kWh and side-by-sides used nearly 606 kWh.
Cold Air Falls
Refrigerator-freezer combos are connected, insulated boxes that are cooled by a refrigerant, which is compressed from warm gas to cool liquid and back again as it is pumped through coils on the back of the appliance. The heat produced by this process transfers to the coils and releases into the kitchen air behind the fridge or at the bottom of it. Fans channel cold air from freezer to refrigerator through ducts and back to the freezer for cooling.
Refrigerators with top-mounted freezers need less help from fans to move cold air from freezer to refrigerator, the Choice website says, because cold air falls. It adds that bottom freezers are located next to the refrigerator's compressor, which produces lots of heat, so more energy is needed to keep the bottom freezer cold. A top freezer is less affected by the compressor's heat.
Nevertheless, the California Energy Commission notes that both are more energy efficient than side-by-side models. Side-mounted freezer models have two vertical compartments. One is the refrigerator and the other is the freezer, which usually has through-the-door ice and water dispensers. The CEC says these dispensers increase a refrigerator's energy usage 14 to 20 percent. But sometimes double-door models are more convenient for consumers.
However, consumers need to consider a number of issues beyond energy use when buying a refrigerator, such as storage space and ease of use. Models with top-mount freezers typically have more storage space. Similar to bottom freezer models, their refrigerator shelves are wide enough for pizza boxes. But consumers access the refrigerator compartment more frequently than we do the freezer. Some find it awkward to stoop down to find what they need in the refrigerator, and thus they prefer refrigerators with the freezer compartments at the bottom. Others like the compromise the side-by-side arrangement allows, its dispenser features and the way its narrower doors work in smaller kitchens despite its narrower shelves.