I'm seeing it peak around the evening in all time zones. This is the link to the actual energy grid visualization tool: https://www.eia.gov/electricity/gridmonitor/expanded-view/el...

Browsing the last day's energy usage yields peaks at:

Eastern: 8pm

Central: 7pm

Mountain 6pm

Pacific: 5pm

Due to AC usage, electricity demand tends to be much higher in the summers than in the winters. And the demand profile in the summers peaks in mid-late afternoon. i.e You are not looking at the highest overall peak of the year, just the hourly peaks from the last few days.