This brief thermodynamic analysis theoretically explores the potential of using a solid-state electrochemical heat engine (EHE) to continually harvest waste heat from available thermal energy from natural and man-made sources. These EHE systems are composed of a fuel cell hybrid (FCH) and an electrolyer hybrid (EH) which is composed of fuel cells and heat engines, and electrolysers and heat engines, respectively. These systems electrochemically utilize reversible working reactions (WR) in a manner to produce electrical energy from thermal energy. Ultimately, EHE’s in this paper exploit the change in basic thermodynamic properties with temperature. This development introduces the thermodynamic methodology for analyzing and combining EHE’s.