In this article, the optimum operating mode of a solar photovoltaic/thermal (PV/T) air collector in terms of exergy losses is obtained. An experimental setup for a typical PV/T air collector is built to measure its thermal and electrical parameters, experimentally. A computer simulation program based on improved thermal and electrical models is also developed to simulate the thermal and electrical parameters of PV/T air collector. Furthermore, a new equation for the exergy efficiency of PV/T air collector based on exergy losses is obtained. Finally, exergetic optimisation and parametric studies have been carried out. It is observed that the results of numerical simulation are in good agreement with the experimental measurements and the new exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature. The optimised values of inlet air velocity, flow duct depth and the maximum exergy efficiency have been also obtained. [ABSTRACT FROM AUTHOR]