人们希望有一个可以商业化使用的数字，向消费者表明各种尺寸、类型和品牌家用冰箱的相对运行经济性。如今，家用冰箱的尺寸从8立方米到20立方米不等。英尺（23立方米）至25立方米。英尺（7升立方米）。用于冷冻柜的空间从不足五分之一到超过三分之一不等。这两个变量都会影响冰箱的能耗。引文:研讨会，ASHRAE交易，第83卷，第一部分，伊利诺伊州芝加哥

It is desirable to have a number that can be used commercially to indicate to consumers the relative operating economy of various sizes, types and brands of household refrigerators. Today domestic refrigerators come in sizes from 8 cu. ft. (.23 m3) to 25 cu. ft. (.7l m3). The amount of this space devoted to the freezer varies from less than one fifth to more than one third. Both of these variables affect the energy consumption of the refrigerator.