> Demand is usually the highest when PV output is also the highest

Not quite, the mismatch in timing between solar generation and energy demand has been called the "duck curve" [1][2]. Peak demand is normally in the evening when people are done with work [3].

[1] https://www.energy.gov/eere/articles/confronting-duck-curve-...

[2] https://en.wikipedia.org/wiki/Duck_curve

[3] https://www.eia.gov/todayinenergy/detail.php?id=42915