Abstract: The variety of energy-using appliances leads to different energy relationships.In this paper,a general representation of the energy relationship of an energy system was illustrated,then general expressions of efficient energy output and energy loss were deduced.Moreover,the influences of proportional links,energy-storage links,feedback links,etc.on efficient energy output of energy-using sysfem were analyzed.This paper provides a theoretical basis for the future analysis of specific energy-using system,and is on benefit to make the targeted energy-saving strategy.

Key words: energy system, proportional link, energy-storage link, feedback link