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. This work is supported by National High Technology Research and Development Program of China (863 Program) (No. 2012AA050201).