To make a rough estimate, you can follow these steps:

1. Determine the energy consumption of your electric car per kilometer. This is usually expressed in kilowatt-hours per kilometer (kWh/km). You can find this in the specifications of your car or by looking up information about your car model.
   
   

2. Estimate the number of kilometers you drive per day. This may vary based on your driving habits and daily travel patterns.
   
   

3. Multiply the energy consumption per kilometer by the number of kilometers you drive per day. This will give you the daily energy consumption of your car.
   
   

4. To determine how many solar panels you need, you must consider the average daily sunlight in your region and the efficiency of the solar panels. The average efficiency of solar panels varies, but for this calculation, let's assume an efficiency of 15%.

   Suppose your car consumes 15 kWh daily and you have an average of 4 sun hours per day in your region. To fully meet your car's energy needs, you would need approximately 15 kWh / 0.15 (efficiency) / 4 (sun hours) = 62.5 kWh of solar energy per day.
   
   

5. To calculate the total capacity of the required solar panels, you need to know how much energy a solar panel can generate. This can vary depending on the power of the solar panel. Let's assume a solar panel has a power of 300 watts.

   The total capacity of solar panels you need then is 62.5 kWh / 0.3 kW (power of a solar panel) = approximately 208 solar panels.

It is important to note that this is a rough estimate and that there are other factors that can affect the performance and efficiency of the solar system, such as shading, panel orientation, and inverter efficiency. Additionally, it's also possible to supplement your car’s energy needs with electricity from the grid when the sun does not provide enough energy.

It is advisable to consult a professional installer to assess your electric car's specific energy needs and the potential for solar energy in your particular situation.