California can't use all its solar power. That's a problem (opens in new tab)

Storage is what is alleviating pressure causing excess curtailment. Excess curtailment is a function of battery deployment rate (transmission too). Only recently has battery storage scaled to catch up to existing solar deployments and the deployment trajectory.

> CAISO’s recent relative curtailment downtick could be due to several factors besides batteries, such as weather conditions and new transmission lines. Still, grid storage battery deployment has undeniably been an important element. CAISO’s addition of over 2.4 GW of battery storage capacity from June 2023 through the end of the year coincided with a sharp reduction in curtailment.

> CAISO is set to continue deploying even more batteries in 2024. The US Energy Information Administration’s latest estimates suggest it will install nearly 5 GW of incremental battery storage capacity in 2024, along with 3.5 GW of new solar photovoltaic capacity. While not every project in queue will ultimately move forward, CAISO’s absolute increase in battery capacity and its relative rise as a percentage of solar capacity will mitigate curtailment.

> More encouragingly, it’s early innings in the rise of batteries. While lithium-ion battery technologies are most prevalent on the grid today, other advances are possible. Most deployed batteries today, such as lithium-ion batteries, have storage of around four hours or less. New technologies, such as iron air batteries, could provide multiday storage solutions. As the quantity and quality of battery deployments improve, the grid will become more resilient and, all else being equal, solar generation’s share of the electricity grid will continue to grow.