Excellent point. Peak electricity consumption occurs during the evenings when solar is producing little, if any, electricity. Daily fluctuations of electricity usage put an even greater demand on electricity storage.

That's not correct, peak demand is usually during mid-day, at least in the US:

https://www.eia.gov/todayinenergy/detail.php?id=27212

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.