The amount of solar panels depends on how much you drive per year, the kWh kilometer consumption and the yield of the solar panels. To determine how many solar panels you need you can use the following formula;
(Number of kilometers per year / The KWh consumption of the car per kilometer)/KWh yield 1 solar panel= number of solar panels,
In general, a 100% Electric car will need 8/9 solar panels.                                          And a hybrid car 4/5 solar panels.