The short answer: about 16 panels.
The long answer:
Solar panels are measured in Watts, a small one is 100W and a large one about 400W Depending on your location and time of year, you get about 5 hours of sunshine in summer and 2 hours in winter.
According to data from the U.S. Department of Transportation, the average American driver drives a little less than 2,000km per moth. A Tesla model 3, one of the most efficient electric cars to date, uses about 16 kWh for every 100 km for a total of 320 kWh a month or just over 10 kWh a day
So the average American driver would need to generate 10kwh per day to charge their car and assuming winter time at 2 hours of sunshine, you would need 5kW of solar or about 16 panels.
A s for economics, a system that size would costs 1.53 a day to produce enough electricity to charge your car in winter(14,000 dollars over 25 years) Gasoline costs 65 cents per liter and the most fuel efficient car made in the US does 6.8 liters per 100km or 4.42 per day.