With 120 million household refrigerators and freezers in operation in the United States, their consumption of electrical energy is of major concern not only to the consumer, but also to the power generating utilities that have to provide the power. The government, charged by Congress with guarding against air pollution, protecting the Earth's ozone layer, and fighting global warming, has a keen interest in refrigerator energy consumption.

Vapor compression, absorption refrigeration (instead of electric power, uses heat as the source of energy), and thermoelectric refrigeration (the direct conversion of electrical energy to cooling effect), are the principal means of refrigeration. Of the three methods, vapor compression, often referred to as mechanical refrigeration, is the most energy efficient, approximately two times more efficient than absorption refrigeration, and four times more efficient than thermoelectric refrigeration. Vapor compression is by far the most popular means for refrigerating household...