This paper deals with the analysis of hybrid photovoltaic thermal (PVT) water collectors under constant collection temperature mode unlike constant flow rate mode. The analysis has been carried out in terms of thermal energy, electrical energy and exergy gain for two different configurations namely case A (collector partially covered by PV module) and case.B (collector fully covered by PV module). The results are compared with the conventional flat plate collector (FPC). The effect of collector area covered by PV module on the performance of hybrid PVT water collector has been studied. The characteristic equations have also been developed for both the cases. It has been observed that case A is more favorable for thermal energy point of view, while case B is suitable for electricity generation. On the basis of the numerical calculations the annual thermal energy gain is found to be 4167.3 and 1023.7 and annual net electrical energy gain is 320.65 and 1377.63 for cases A and B respectively. The annual overall thermal energy gain is decreased by 9.48% and an annual overall exergy gain is increased by 39.16% from case A to case B. (C) 2013 Elsevier Ltd. All rights reserved.