Fuel consumption and CO2 emission regulations for vehicles, such as the Zero Emission Vehicle (ZEV) Regulation, motivate renewable energy technologies in the automotive industry. Therefore, the automotive industry is focused on adopting solar charging systems. Some vehicles have adopted solar energy to power the ventilation system, but these vehicles do not use solar energy to power the drivetrain. One important issue facing the design of solar charging systems is the low power generated by solar panels. Compared to solar panels for residential use, solar panels for vehicles can’t generate as much power because of size and weight limitations. Also, the power generated by solar panels can be extremely affected depending on differences in solar radiation among the cells. Therefore, Toyota has developed a solar charging system that can use solar energy for driving the Prius PHV. This system can efficiently charge the hybrid battery with the low power generated by the solar panel. The power generated can charge the hybrid battery while the vehicle is parked. Power can also be supplied from the hybrid battery to the auxiliary battery system during driving. The solar power contributes to the improvement of the electric driving range and the fuel consumption. This paper shows a solar charging system applied to a plug-in hybrid vehicle, a system configuration, operating modes, improving the standby power consumption of the system, and structure of solar panel.