This paper develops a general model to analyze the performance of thermoelectric generators (TEGs) with consideration of their side surface heat convection (SSHC) and temperature-dependent material properties. The closed-form solutions of temperature field and energy conversion efficiency are derived, and the analytical results agree well with numerical results as well. These explicit expressions can be used to evaluate the performance of TEGs under various boundary conditions directly. Based on the derived expressions of temperature and efficiency, we find that the optimization of a TEG module can be attributed to only three parameters. Through an example, we give some useful suggestions for the design of high-performance thermoelectric modules. (C) 2019 Elsevier Ltd. All rights reserved.