Abstract: Based on the second law of thermodynamics，a method of energy consumption evaluation of electrohydrodynamics(EHD) enhancement of heat transfer was presented, the profit factor of available energy was newly defined.The experimental data were analyzed. The results showed that the profit factor of available energy increased with increasing heat flux under the same voltage given in experiments, while decreased with increasing voltage under the same heat flux given in experiments.It was found for the first time that the application of EHD enhancement of heat transfer was not economical when the voltage was higher than a critical value at a low heat flux. This method provided a theoretical basis for the economy of EHD heat transfer enhancement.