Refrigerators that are more than 15 years old as of 2014 weigh as much as 250 pounds. More-recent models weigh around 200 pounds and have some parts that can be removed when moving the units.
To keep food from spoiling, a refrigerator must maintain a temperature between 37 and 41 degrees Fahrenheit. Food is kept in an insulated space, and cooling is provided by a heat pump.
Before the invention of the refrigerator in 1913, ice houses and ice boxes were used. They are still used in some areas of the world as of 2014. The first widely used refrigerator was the Monitor-Top model introduced by General Electric in 1927.