Abstract: By referring to the utility theory in economics,the concept of power utility is proposed.Based on traditional energy efficiency evaluation,power utility is intended to characterize the value of the power used by the consumer in his capacity as subject,which plays a key role in energy-saving and demand response.Firstly,based on the typical electrical appliances’classification results,different electrical appliances’temperature and time utility functions are given.Secondly,the power utility grading theory of residential electrical appliances is put forward,and application of the energy saving and demand side management is expounded.Finally,with the typical family environment as an example,the appliances’power utility level is evaluated,which proves that higher utility grade means lower energy consumption.