Batteries, Power-Sharing Struggle with California's Green Energy Growth

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Written by Paul Wiseman for IIR News Intelligence (Sugar Land, Texas)

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Summary

California's wind/solar curtailments hit a record high in April, while solar generation surpassed natural gas for first time for the first half of the year.

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California's Green Energy Dilemma

For wind and solar power in California, it's too much of a good thing. Solar curtailments set a record in the state in 2024, according to the U.S. Energy Information Administration (EIA).

The California Independent System Operator (CAISO) curtailed 3.4 million megawatt hours (MWh) of utility-scale wind and solar output, which was 29% more than in 2023. Of that, solar was hit the most, accounting for 93% of all CAISO's curtailments.

April also saw record-high renewables curtailment in the state, at 1.6 MWh, according to a June 15 post from Lucas Davis in his Energy Institute blog. That number is equivalent to 18% of all grid-scale wind and solar generation for the month.

These growing issues come despite furious efforts to add battery energy-storage systems (BESS) and to trade power with nearby states through the Western Energy Imbalance Market (WEIM), a stand-alone market platform for balancing ISO authorities in the U.S. West.

Industrial Info Resources is tracking 117 battery energy-storage system (BESS) projects across California, totaling nearly $50 billion of investment, with completion dates spanning 2026 to 2030.

Industrial Info Resources offers more information on these projects in its Global Market Intelligence (GMI) Power Project Database, where readers can find details--including construction schedules, investment values and necessary equipment--in a list of project reports.

Most of the solar curtailments in 2024 and earlier happened in the spring when, as the EIA points out, the California sun is blazing but power demands are lower than they are in the hot summer months.

By the Numbers

• 3.4 million: MWh of wind and solar generation curtailed by CAISO in 2024, up 29% from 2023
• 93%: Solar's share of that curtailment in 2024
• 15 GW: Total BESS capacity in California in 2026, up from just 0.5 GW in 2020

With Great Power Comes Great Management Responsibility

Renewable generation in California has grown exponentially over the last 10 years, says the EIA. In 2014, it showed California with a combined 9.7 GW of wind and solar photovoltaic capacity. By the fourth quarter of 2024, the number was almost triple, at 28.2 GW.

That growth has let solar alone surpass natural gas with increasing regularity in CAISO, says the EIA. Utility-scale solar outproduced gas on 82% of days in January to May 2026, compared to 21% in the same period in 2024 and 2025.

To manage that growth, expanding the power grid is a necessity. But the hurdles there include massive investment, right-of-way procurement and power purchase contracts, among others.

Indeed, grid expansion is underway in California. But as noted by research firm Grid Flexibility, the state also is greatly expanding BESS installations to manage the random intermittency of wind and solar, getting them closer to baseline reliability.

"California scaled one of the largest battery fleets in the U.S. by procuring it)," said Grid Flexibility. Grid storage went from about half a gigawatt to roughly 15 GW in six years (2020-2026).

Grid Flexibility listed three state-level tools California used to achieve this growth: "a state mandate that ordered the capacity, a resource-adequacy payment that pays it every year, and financing. Batteries now carry much of the 4-to-9 pm evening ramp that solar's midday surplus creates."

Also, Grid Flexibility notes that about 41% of CAISO' current utility-scale solar is co-located with BESS. That number will rise with new development, as 93% of solar projects through 2030 will be co-located with BESS.

Power Trading Another Option

One reason the EIA gives for solar's concurrent rise in generation capacity and curtailment is that CAISO juggles a significant list of power options to get the best prices.

While solar curtailments were rising, imports from nearby systems doubled. The EIA says the increase was driven by relatively inexpensive generation from several sources.

Among the reasons for greater imports is an easing of drought conditions in the Pacific Northwest, which gave that region some low-cost export capacity. Also, in April 2026, CAISO began importing low-cost power from New Mexico's new SunZia wind project near the city of Corona.

According to Industrial Info Resources data, SunZia's design capacity is 3,515.4 MW, with a startup date of April 30, 2026. Readers can learn more from a detailed plant profile.

Power sharing through WEIM originated in 2014 as a partnership between CAISO and PacifiCorp. Its purpose is to expand real-time wholesale energy trading and automated grid balancing across the Western Interconnection, which spans Canada to Mexico and from the Pacific Coast to the U.S. Midwest.

The stated goal of trading through WEIM is not only to import, but also to export excess solar and wind power. However, the EIA data seems to show that a true balance is yet to be achieved, at least in California.

The Bigger Picture

California is hardly alone in its dilemma of matching takeaway with generation from a wide variety of sources. Most power systems across the U.S. and around the world share this dilemma.

Key Takeaway

• As with many grids worldwide, it's one thing to generate clean power, it's another to deliver it when and where it's needed. Growth in both BESS and grid connections currently lag far behind growth in generation in California and elsewhere.

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About Industrial Info Resources
Industrial Info Resources (IIR) is the leading provider of industrial market intelligence. Since 1983, IIR has provided comprehensive research, news, and analysis on the industrial process, manufacturing, and energy-related industries. IIR's Global Market Intelligence (GMI) helps companies identify and pursue trends across multiple markets with access to real, qualified, and verified plant and project opportunities. Across the world, Industrial Info Resources is tracking over 250,000 current and future projects worth $30.2 trillion (USD).