https://pvwatts.nrel.gov/

plug in a prototypical 1000W PV system at your latitude and longitude, as if it's on the roof of your house. That would be four 250W panels.

Look at the kWH produced per month in mid summer, and again in mid winter.

Using Seattle as an example, estimated production of 147kWh per month in mid summer, and 34kWh in the worst month of winter.

Now look at how many kWh the capacity of a tesla battery (70 or 90 or 100kWh) is for a single full charge.

147, divide by 31 = 4.74kWh per day

Those estimate figures for pvwatts are pretty rough, but they also calculate based on having near direct sunlight from sunrise to sunset, as if the PV panels are on the roof of a building or an unobstructed ground mount. Cars are frequently in the shade.

Realistically, if you were to somehow magically cover a Tesla in 1000W of PV, and it was all flat-angled optimally to catch the sun, you might get 3kWh a day if you were really lucky.

There is really no practical reason why the photovoltaics needs to be ON the car. Putting high efficiency pv cells on curving surface is expensive and hard. The PV can be on a roof mount covering your closest grocery store, home depot, car repair garage, public school, and so on, feeding the grid.