In order to prevent hydrate forming in city gate stations (CGS), natural gas is preheated before pressure reduction. In this work, employing combined heat and power (CHP) technology in CGSs, by which the required heat is provided and electricity is freely produced, is comprehensively studied to answer this main question that which CGS is an appropriate host for CHP technology. In this respects, a comprehensive thermo-economic analysis was accomplished on several CGSs of Iran to firstly, find the most optimal CHP system size and design for each station and secondly, define a general criterion by which one could realize that if a CGS can efficiently employ CHP technology. Net present value (NPV) approach is used to analyze and compare the performance of these stations economically. The results showed that only one of the case studies can hire CHP system efficiently. It was conceived that utilizing CHP system is more efficient if it works at higher power ranges. Therefore, considering the effective parameters on heating demand of CGSs, the novel criterion of RHD was introduced as the target index of this work. Finally, the results demonstrated that CGSs with RHD values greater than 0.23 are suitable for using CHP systems. (C) 2016 Elsevier Ltd. All rights reserved.