With the rapid expansion of urban road networks and the increasing ownership of vehicles in many countries and regions, the greenhouse gas and pollutant emissions from road travels have become a global concern. The introduction of electric vehicles (EVs) with dynamic charging into road systems, which is defined as electric road systems (ERSs), has been widely recognized as a viable solution to address this problem. This paper presents a comprehensive study on the reliability of power supply systems integrated with renewables for ERS (ERS-PSRs), which interface with both road traffic and power networks. First, a brief introduction to the charging modes of EVs demonstrates the coupling of the two networks. A simplified traffic model is then built, based on which the reliability indices of the system considering the influence of the dynamic charging and static charging modes of EVs are proposed. Further, a simplified trip chain based Monte Carlo reliability assessment method of ERS-PSRs is proposed. Case studies based on the IEEE Roy Billinton Test System (RBTS) show that the dynamic charging mode of EVs can not only effectively balance the supply and demand of the power grid at different time (shaving peaks and filling valleys), but also significantly improve the reliability of ERS-PSRs. The case studies also examine the effects of the ratio of EVs with dynamic charging, wind generation penetration rate, additional wind power, and battery energy storage systems (BESSs) on the reliability of ERS-PSRs.