In this paper, the performance study is performed in order to verify the new design of the photovoltaic (PV) panel combined with type of the wickless heat pipe solar water heater. In this enhanced design, each wickless heat pipe is assumed in the shape of the loop mini tube comprised of the flow boiling process inside it. Without considering the PV panel, this design was reported in our prior published work (Ziapour et al., 2016). Here, the performance of the proposed passive PVT solar collector is numerically performed using EES software. The solar cell packing factor (i.e. fraction of the absorber plate area which is covered by the solar cells)is important parameter for designing a PVT system. The simulation results show that the thermal efficiency of the passive PVT solar system increases with increase of the solar cells packing factor. Through the simulation results it is found that the optimal numbers of the wickless heat pipes may be five loops. By selecting the five loops, the maximum value of the tank water temperature is obtained near to 72 degrees C in the evening. Also the maximum values of eta(th) and eta(pv) are found as 70% and 80% at noon time, respectively. (C) 2016 Elsevier Ltd. All rights reserved.