Low bandgap TPV cells are preferred for electric power generation in TPV cogeneration systems. Recently, significant progress has been made in fabrication of low bandgap semiconductor TPV devices, such as InGaAsSb and InGaAs cells. However, it appears that only limited data are available in the literature with respect to the performance of these TPV cells in combustion‐driven TPV systems. In the research presented in this paper, power generation using recently‐developed InGaAsSb TPV cells has been investigated in a gas‐fired space heating appliance. The combustion performance of the gas burner associated with a broadband radiator was evaluated experimentally. The radiant power density and radiant efficiency of the gas‐heated radiator were determined at different degrees of exhaust heat recuperation. Heat recuperation is shown to have a certain effect on the combustion operation and radiant power output. The electric output characteristics of the InGaAsSb TPV devices were investigated under various combustion conditions. It was found that the cell short circuit density was greater than 1 A/cm2at a radiator temperature of 930°C when an optical filter was used. An electric power density of 0.54 W/cm2was produced at a radiator temperature of 1190°C. Furthermore, modeling calculations were carried out to reveal the influence of TPV cell bandgap and radiator temperature on power output and conversion efficiency. Finally, the design aspects of combustion‐driven TPV systems were analyzed, showing that development of a special combustion device with high conversion level of fuel chemical energy to useful radiant energy is required, to improve further the system efficiency. © 2003 American Institute of Physics