This isn't true. The peak demand that remains after solar has lowered the actual peak, is in the evening.

And that's when you use hydro and batteries.

Here's the historical yearly peaks: https://www.caiso.com/documents/californiaisopeakloadhistory...

Note, in recent years this ignores home based solar, which also reduce the grid seen demand during the day, but the new peak is still before sunset.

The local grid refers to this post solar/wind demand as 'net demand peak':

> Net demand is the total electricity demand minus utility-scale solar and wind generation at a given time, and the net demand peak (the “net peak” for short) typically occurs later in the evening than the total demand peak.

https://www.energy.ca.gov/data-reports/energy-insights/peek-...

> Initially, net demand peaked around the same time as total demand. Wind, which tends to pick up in the evenings, was responsible for most of the renewable generation. In 2013, solar began to eclipse wind. By 2016, the average timing of the net demand peak shifted from before 5:00 p.m. to around 7:30 p.m., where it has remained. (The total demand peak has also moved later in the evening to a lesser extent, driven by customer-owned solar.) Grid operators can’t turn to solar after the sun sets to meet the resulting net peak.

Luckily California has big plans for offshore wind, but that'll take about a decade. In the meantime solar and demand management is probably still the low hanging fruit.