Indium gallium arsenide (InxGa1−xAs) cell models extracted from measured data on thermophotovoltaic (TPV) cells with bandgaps of 0.75 to 0.55 eV are presented. The dark current model is based on a fit to values extracted from open‐circuit voltages at high photocurrents (where the ideality factor is close to unity) for the various bandgap cells. Quantum efficiency models of Hovel and a very simple base model are compared with measured data. A standard model for the series resistance of the cell is presented and agrees with measured data. The quantum efficiency model is used with the standard blackbody equations to predict the cell photocurrent at 800 and 1200 C over the 0.5 to 0.75 eV bandgap range. The dark current, series resistance, and photocurrent are used to numerically determine maximum output power for InxGa1−xAs cells over the above bandgap range at these two blackbody temperatures. ©1996 American Institute of Physics.