I think it is interesting, and I didn't know the Sonata had this option.
This is apparently the potential for the 2020 Sonata's Solar Roof Option: "potentially a couple of miles of extra engine-off distance from six hours out in the sun, and up to 700 “free” miles back per year."
Like all these systems, it depends on how much sun you get, how much it costs the customer and manufacturer, and what you define as useful.
https://www.greencarreports.com/news...ing-solar-roof