The solar irradiance outside the earth’s atmosphere is 1 kW/m2. Putting in the various losses such as atmospheric attenuation, off-normal angle due to latitude, and photovoltaic conversion efficiency, the required area of a solar cell panel is about the same as a double garage door to get 1 kW. It must be a very clear day at high noon to get 1 kW. Further the solar panel must be clean; dirt on the surface further reduces power. Is your car always clean? With a reasonable area, the power from solar cells is about a factor of 8–10, too small for meaningful hybrid propulsion. However, solar cells have a place. See the solar-powered cabin cooling fan used in the Ford Reflex concept car Assume your hybrid is not at home during the day. Instead of having solar cells installed on the car, put the cells on the roof of the garage or house. During the day, electrical power is generated. What can be done with the daytime-only power? Two choices exit. First, charge batteries at home; these batteries are a second set not installed in the hybrid or EV. Then charge the hybrid batteries at night from the second set of batteries. Not a great idea. Second, sell the daytime power from the solar cells to local utility. Then at night buy the power to recharge the hybrid batteries.