Couple of points…
While unique in geography, WA state has the highest capacity hydro enterprise in the country, and its very reliable.
Storage isn’t limited to batteries. Grand Coulee uses excess capacity to pump water upstream to Banks Lake during off-peak use, then uses that potential energy to augment during peak use. A similar, though much smaller system is being built here in Kauai, but with solar, pumping water uphill during the day to generate power at night.
Finally, if I can brag on my installation for a moment, the Navy partnered with the Kauai electric utilities to build a 20 megawatt solar PV farm on Navy land at PMRF, which went operational this summer. The base has first dibs on the PV power if normal service is interrupted. Last week, we ran 100% of our base electric demand off of our PV system for about 7 hours when a power line went down off base. Pretty cool.