In this work an approach to select equipment modules for a flexible modular production plant at low investment costs using a multi-objective evolutionary algorithm is introduced. Thereby, a good determination of the plant's overall operating window is of utmost importance. A styrene production plant serves as case study to evaluate the equipment module selection approach, to analyze the resulting compromise solutions as well as the flexible modular equipment sets with low investment costs. It is for example possible to achieve an 11-fold enlarged operating window for 50% higher investment costs compared to the conventional design. Thus, this work presents an important step towards the realization of modular production plants. (C) 2018 Elsevier Ltd. All rights reserved.