To make the building energy performance certificate more effectively, it is necessary to analyze the historical trends in the energy performance of existing buildings as well as their current status. To achieve this objective, this study aimed to develop a dynamic energy performance curve for evaluating the historical trends in the energy performance of existing buildings using a simplified case-based reasoning (S-CBR) approach. Based on the relationship between the historical trend in the energy performance of a given building and the generalized historical trends (which can be established using the developed S-CBR model), the four types of the dynamic energy performance curves were established. To validate the applicability of the dynamic energy performance curve, an elementary school facility located in Seoul, the capital of South Korea, was selected for model application. The developed dynamic energy performance curve can be used to make the public clearly aware of the historical trends in their building's energy performance, to establish the optimal energy retrofit strategy for their buildings, and to encourage the public to voluntarily participate in their country's energy-saving campaign. (C) 2015 Elsevier B.V. All rights reserved.