Efficient energy and its conservation is a great challenge for engineers. All the refrigeration and air conditioning machines consume large amount of electrical energy. To minimize its consumption various technologies are working day and night. As far as government of India is concern, it already started special norms which are standardized by BEE (Bureau of Energy Efficiency). Energy Standards are becoming more stringent and to meet up with them it is necessary to make refrigerators more energy efficient. Energy saving can be done either by optimizing subsystem related to cooling or Defrosting. Commercial refrigerated display and storage cabinets normally use one of five defrost method. Condensing unit off permitting natural defrost along with Hot gas defrost, Electric defrost, Water defrost and Other external heat source defrosts. The refrigerators described here are used in supermarkets to display and store perishables products. Focusing here on hot gas defrosts method & its energy benefits over the convention methods like electrical heater method. Main emphasis has been given on defrost cycle of No frost Refrigerator. It is meaningful to note that the defrost efficiency is compressor discharge temperature by optimizeding discharge temperature.