The purpose of this study is to develop a novel method for the energy‐saving diagnosis of user‐side scene lighting. The method is not only to calculate the potential of high‐efficiency lamps instead of traditional lamps but also to modify the simulated correctness of the reconstructed field via the spatial field reconstruction and the environmental parameters. Moreover, it will compare the results before and after the lamps change from numerical simulations, and recommend the possible suggestions according to the Chinese National Standards (CNS) recommended lighting level. The main contribution of this study is that users can dispel the doubts about the investment benefits of lamps replacement and the sacrifices of the illumination of the field, as well as the lack of both the traditional lighting and the ambient lighting. In addition, the effectiveness of the proposed energy‐saving diagnosis method of scene lighting in comparison with a traditional lighting analysis method is verified by a specific restaurant case. The proposed novel lighting analysis can save 37% energy consumption and shorten 58.4% payback time than the traditional lighting analysis. Furthermore, this study analyzes 38 small and medium enterprises (SMEs) in Taiwan to explain the benefits of the proposed energy‐saving scene‐lighting diagnosis mechanism. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13058, 2019