This has maps that show where power plants are located, by type:
https://www.washingtonpost.com/graphics/national/power-plants/
“SHARE OF ELECTRICITY GENERATED BY NATURAL GAS-POWERED PLANTS”[by state]
A Tesla in West Virginia will probably get recharged using coal.
A Tesla in Rhode Island is unlikely to get recharged using coal.
Guess the Southern state most fond of solar-generated utility electricity as of 2017.
https://www.washingtonpost.com/graphics/national/power-plants/