Refrigerators and freezers come in all styles. Mr. Sachs said that each has its own advantages and disadvantages. For example, he said, "a two-door, side-by-side refrigerator probably is going to be less efficient and less convenient than a similar-size model with a bottom or top freezer." One reason: the side-by-side has a relatively larger freezer volume at a much colder temperature -- and a larger surface area from which the cold air can escape.
Special conveniences can also affect efficiency. For instance, refrigerators that offer ice and chilled water through the door use more electricity, Mr. Sachs said, partly because there is less insulation in the door.
He advised looking beyond the ratings: "Especially where electricity is expensive, try to go well beyond Energy Star's minimum requirements."