Understanding the power and energy performance of supercapacitors connected to constant power elements is important for many applications. This paper proposes a characterization method for two supercapacitor models that are used to analyze the power and energy behavior of supercapacitors connected to constant power elements: linear capacitance model and constant capacitance model. The linear or constant capacitance is determined by conducting a constant power experiment. A set of constant, power experiments is designed. The proposed method can reduce the error in estimating the constant power experiment time for a variety of supercapacitor samples with different rated capacitance and voltage. The accuracy of using the linear capacitance model and the constant capacitance model is approximately equal. Moreover, the performance evaluation results suggest that using the linear or constant capacitance fitted through a low power discharge experiment can minimize the error, which can serve as a guideline to design the constant power experiment. (C) 2016 Elsevier B.V. All rights reserved.