California still imports a large amount of power from other states (primarily Arizona and Utah, with some hydro from Oregon). So we essentially outsourced a lot of our power production to other states.
Transmission is crucial for flexibility in balancing generation and consumption, as well as optimizing storage utilization. You can also assume there will be times you’ll throw away (curtail) clean energy as it’s cheaper than it would’ve been to store and then deliver it, but you still need that capacity available at other times (seasonal variability).