In the present study a novel thermal model for a PV/T system is developed which includes the thermal contact resistance between the layers of a PV/T system and individual resistance of the layers. This model provides a clear understanding of how the properties of individual layers of a PV/T module influence its overall performance. The developed model is quite detailed and therefore it will be useful to precisely analyse newly developed tube and sheet PV/T systems. The present model has been compared with an earlier model developed. It is further validated using the present experimental data. It is observed that both the experimental and simulation results of the developed model are in good agreement. The Root Mean Square Errors (RMSE) of 3.75 K, 1.36 K and 2.71 K were reported for the water outlet temperature, glass surface temperature and cell temperature, respectively. The present numerical simulation results illustrate that consideration of thermal contact resistance and Ohmic loss at PV layer reduces the errors significantly. It has been reported from the present experimental study that the electrical, thermal overall energy and exergy efficiencies vary from 12.24-13.02%, 18.16-41.83%, 19.1-28.9% and 8.89-10.03% respectively.