A single 250 Watt solar panel can produce about 1 KWh per day in the US (a little more or a little less depending upon the part of the country and the aim). 20

A single 250 Watt solar panel can produce about 1 KWh per day in the US (a little more or a little less depending upon the part of the country and the aim). 20 of them would produce about 20 KWh. That ends up being between 60-80 miles of daily electric range for ~30 years. The panels themselves cost about $125 each, with a total panel cost of $2500. Unfortunately, installed costs will likely get you closer to $16,500 for this whole setup. Over the lifetime of the panels, you would expect over 600,000 miles worth of production. The equivalent amount of gasoline (assuming 36.5 mpg and 2.50/gallon) would be 41,000. Feel free to check my match, and Of course, I'm handwaving around some problems (the time value of money for one), but I think it is pretty easy to see that there are viable options for vastly increasing the amount of power production available and to do so largely in lockstep with the increase in demand for power from electric vehicles. I think it is also pretty easy to see how a Tesla salesman might frame a sales pitch for solar panels.