Top-freezer refrigerators are usually more efficient than comparable bottom-freezer refrigerators. Top-freezer designs are also more efficient than side-by-side refrigerators, consuming an estimated 10 to 25 percent less energy than bottom-freezer or side-by-side models.
The primary reason for the higher efficiency of top-freezer refrigerators is the location of the refrigerator's compressor. Most modern refrigerators place the compressor at the base of the refrigerator. Because the compressor generates significant heat when cooling the refrigerator, locating the freezer at the top of the appliance means less heat reaches the freezer as compared to other designs. Therefore, less energy needs to be expended to keep the freezer's temperature low.