This paper presents a parametric study of thermophotovoltaic (TPV) system efficiency and output power density based upon a simple model of the TPV system. The efficiencies presented here are based on thermodynamic limits. Some issues relating to the choice of TPV materials are considered. It is shown that the optimum TPV cell band gap depends not only on the emitter spectrum, but on the type and effectiveness of the spectral selection. Trade‐offs between efficiency and output power are also illustrated. In addition, issues associated with creating a more detailed TPV system model are discussed. ©1996 American Institute of Physics.