He mentions that the mega chargers will all be solar powered. I don't know how this will be possible as the user base grows. The amount of energy needed for even a small fleet will be huge.
Tesla semi consumption: One charge: 500 miles => There are about 2 million semi trucks in the US (tractor trailers). Assume that each semi fully charges once a day, 300 days a year.
The conversion of all of the country's semis to Tesla vehicles powered with solar generation requires under 600 TWh a year, eight times current US solar level; still only 15% of current total US electricity generation. Likely within 10 years, or sooner.