Nowadays a topic of most concern is how to protect the global climate change and meet the increasing demand of fresh water. To meet this challenge an intelligent use of energy is urgently needed.

The term “Green Heating System” is synonymous with“Environmentally Friendly Heating System”.This term is academically defined in this paper. To this end the paper introduces the concepts of reversible mode of heating and generalized total heating system which consists of six subsystems, involving three sections, namely “hot end”，“cold end”and “heat generation section”.The exergy - based Specific Consumption Analysis Approach proposed by the author was adopted to quantitatively evaluate the effect of these subsystems on performance of the global system. It is found that emissions caused by heating systems are expected to be enormously reduced as a result of fuel saving potential explored by means of enhancement of exergy efficiencies of the above -mentioned subsystems. In addition, an integration of a large - scale green heating system with sea - water desalination plant will provide an alternative of fresh water supply which could compete with that of water source reallocation projects.