If anyone wants to get a really good view for year to year changes in fuel mix by region, just look for your RTO or ISO's website. ISO-NE, PJM, MISO, SPP, ERCO

If anyone wants to get a really good view for year to year changes in fuel mix by region, just look for your RTO or ISO's website. ISO-NE, PJM, MISO, SPP, ERCOT, & CAISO all track this in real-time and do regular reports on it. These are the entities that watch over large sections of transmission and generation and act as "air traffic controllers" for the grid. They also run the optimization software that chooses which generation runs each day based on minimizing production cost while maintaining reliability. You might have to Google a little bit. In the SPP region, they've seen massive wind penetration and coal has decreased considerably in the last 4 years.