Long knockout trips aren't a forte of electric cars. What they are best suited for are daily needs: get you to work or a supermarket and drive you back home. So how many solar panels do you need if you don't plan to drain your car battery every day?
An American citizen drives around 13,476 miles per year
which translates to roughly 37 miles per day. It's unclear what the exact Tesla Model 3 energy consumption is: on paper it's around 4 miles per 1 kWh, but in reality it's closer to 2.6 miles. Let's go with the latter to have an energy backup just in case. The daily energy need for an EV approximately equals to: 37 mi ÷ 2.6 kWh/mi = 14 kWh
Now let's figure out how many panels we need to generate 14 kWh daily. Assuming we're still in Oklahoma, 14 kWh ÷ 5.6 h = 2.5 kW
Such a solar array can consist of, for example, eight 330W solar panels or nine 300W. This is a reasonable number and indeed somewhat comparable to running an AC unit.
To sum it up, solar panels can and should be used to power up EVs. However, charging a battery from zero takes too long and requires a lot of power. This is why the best strategy is to recharge the battery of an RV in small doses. Consequently, a conventional car is better for long trips, whereas an EV works better in short range. Keep in mind, that solar panels don't work at night. So, if you leave a car to charge overnight, it's going to get energy from your solar battery.