This paper explores the potential of using solid-state electrochemical heat engines (EHE) operating on reversible redox reactions to generate electric power using available thermal energy from natural and man-made sources. Electrochemical heat engines utilize and control the electrochemical potential of molecules undergoing redox reactions in a manner to produce electrical energy from thermal energy. The electrochemical potential of these redox pairs is a function of composition, temperature and pressure. EHE's in this paper exploit the change in basic thermodynamic properties with temperature. The EHE technology can be deployed using fuel cell and electrolyser combinations. It is quite interesting that for mature optimized EHE systems there is great potential for energy harvesting. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.