In this work, a hybrid thermoelectric generator/thermal radiator unit is examined with the aim of producing electricity while heating a cold space. A mathematical model was constructed for the thermoelectric generator, TEG, under steady-state conditions linked with a hydronic heating system. The TEGs were installed on the two sides of the aluminum sheet of the radiator to utilize the temperature difference between hot water inside the radiator and surrounding air. In addition to the TEG parameters, temperature and velocity of hot water and air were considered in assessing the performance of the hybrid system. The performance of the hybrid system was studied and compared under free and forced convection conditions. It was found that a typical radiator produces about 0.849 W of power in addition to the normal heating effect at an air velocity of 0.5 m/s, in addition to the normal heating effect of 1092 W at hot water temperature of 365 K. Ambient air velocity was the most influential on power with optimum value of 0.5 m/s. Moreover, it was found that the power produced decreased by 15.39 % for an increase of 5 K in ambient temperature while the power increased by 24.6 % as the temperature of hot water increased by 5 K. The power generated by such a system may be significantly increased by utilizing large radiation units in addition to enhancing the TEG performance.