Tennesee/Carolinas/Mid-Atlantic: I never realized how much they generate from nuclear.
Central and Midwest: That wind sure does blow!
California and Texas: I love seeing the daily solar spikes, and the corresponding natural gas dips. I think the gray line going negative in California is energy storage being charged up during the daylight hours?
Northwest: Known for hydro! If you narrow in on just the Bonneville Power Administration sub-region (basically Washington/Oregon/Idaho) then it's much more pronounced, and hydro is something like 80% of the generated electricity.