My take on this is if they put up wind or solar arrays, it would work better than trying to charge people's cars live off it.
Have you ever calculated how big a solar array it would take to charge a Tesla battery?
Solar constant on the ground at U.S. latitudes is about 750 Watts/m^2.
High-efficiency panels are about 22% efficient. Commercially, 18% is more realistic, but let's go with 22%.
Solar capacity factor for the desert Southwest U.S. is about 0.18. Multiply by 2 to account for night.
The big Tesla S battery has a 85 kWh.
750 Watts/m^2 * 22% efficiency = 165 W/m^2
times 0.36 capacity factor (average for the day) = 59.4 W/m^2 average generation during the 12 hours of daylight
Assume 90% charging efficiency. Real-life measurements put it at about 85%, but solar would charge it a lot slower so let's be generous and say 90%. At 90% charging efficiency, you need 94.4 kWh to fill the 85 kWh battery.
To charge the battery in 12 hours would thus take:
94,400 Wh / (12 hours * 59.4 W/m^2) = 132.5 m^2 of solar panels
A car parking space is about 9' x 18', or about 15 square meters. So you'd need roughly 9 car parking spaces worth of solar panels to charge one big Tesla S battery per day in the desert Southwest U.S.
Costs of implementing a PV Solar generation system are about $3.30/Watt in the U.S. on a utility-level scale. Technically this is commercial scale, but let's go with best case. 1 m^2 of these panels would be rated at 165 Watts peak capacity. At a price of $3.30/Watt, this would be $544.50/m^2 * 132.5 m^2 = $72,146.25 worth of PV to be able to charge 1 Tesla battery per day.
The amount of electricity used by a busy Tesla battery charging station would put it into the industrial category. The average U.S. electricity price for industrial customers was $0.07/kWh for 2014. At $0.07/kWh, the panels would essentially be charging the battery with $6.61 worth of electricity per day. It would take 10,913 days, or 29.9 years for the PV system to pay for themselves.
I won't go through the math in detail, but if you use more realistic figures of 18% efficient panels, 0.145 capacity factor (average for the U.S. overall), 85% charging efficiency, and the $4.50/Watt cost of commercial PV installations, the numbers end up 213 m^2 (14.2 parking spaces) of panels to charge one battery per day, and 61.9 years before the panels pay for themselves.
The costs are coming down, and we will eventually get to the point where it's cost-effective. But please do a reality check on the notion that you'll be able to prop up a few square meters of solar panels and charge your car for free.