This paper reports single-electrode Peltier heats for cathodic (or anodic) reactions of Li-Si alloy electrodes in coexisting phase states evaluated from their thermoelectric power values. The thermoelectric power and thermodynamic properties for various coexisting phase states in Li-Si alloy were determined from electromotive force measurements of the following nonisothermal and isothermal cells, respectively (T) Li \ LiCl-KCl \ Li-Si (T + Delta T) and (T) Li \ LiCl-KCl \ Li-Si (T). General methods of estimating the thermoelectric power for a lithium alloy electrode from its thermodynamic properties have been developed thermodynamically. The estimation methods were validated by detailed comparison with experimental results of LiSi alloy electrode systems.