CAISO Solar vs Natural Gas Generation Report: EIA Grid Data & Trends

Key Takeaways

• In the first five months of 2026, utility-scale solar generation surpassed natural gas generation across the California Independent System Operator (CAISO) grid.
• Solar generation grew 21% compared with the same period in 2024, while natural gas generation decreased by 60%.
• Solar produced more electricity than natural gas on 82% of days in the first five months of 2026, up from 21% in 2024 and 2025.
• Net battery storage capacity rose 79% to reach 16 GW, while utility-scale solar capacity reached 25 GW.
• Battery storage discharge tripled, smoothing midday solar oversupply into evening net peak demand hours.

Historic Grid Milestone: Solar Surpasses Natural Gas in California

A historic generation crossover took place across California's bulk power system during early 2026. Data published by the U.S. Energy Information Administration from its Hourly Electric Grid Monitor confirms that utility-scale solar electricity generation in the California Independent System Operator (CAISO) over the first five months of 2026 increased 21% compared with the same period in 2024, and natural gas generation decreased by 60%.

This shift was not confined to brief afternoon output spikes. In CAISO, utility-scale solar generated more electricity than natural gas on a daily basis on 82% of days in the first five months of 2026, up from 21% in 2024 and 2025. This structural flip demonstrates that zero-marginal-cost solar generation combined with fast-responding battery storage has displaced conventional thermal peaking plants as the primary daytime generation source.

These wholesale market dynamics directly reflect California's regulatory framework. As the state implemented changes under California CPUC NEM 3 net billing and mandated smart inverter standards under California Rule 21, utility-scale infrastructure scaled in parallel to handle significant intermittent power flows.

Diverging Capacity Paths: Solar and Storage vs Natural Gas

The divergence between clean generation and thermal generation stems from structural changes in CAISO's resource inventory. According to the EIA's Preliminary Monthly Electric Generator Inventory, utility-scale solar capacity and battery storage capacity expanded rapidly over the past two years, while natural gas capacity remained flat.

From April 2024 to April 2026, utility-scale solar capacity increased 19% to 25 gigawatts (GW), and net battery storage capacity increased 79% to 16 GW. In contrast, natural gas capacity remained nearly unchanged at 29 GW. Overall, total net capacity in CAISO increased by 14% (11 GW) during this period.

Because gas-fired plants did not expand while battery storage assets expanded by 79%, solar arrays operating in tandem with grid-scale batteries effectively captured daylight generation and displaced gas generation during the highest price hours.

Battery Storage Tripling and Evening Dispatch

Battery storage plays a pivotal operational role in enabling solar to displace natural gas. As the EIA report details, battery storage charges when solar generation exceeds grid needs in the middle of the day and contributes power to the grid during the evening and early morning when there is less sun.

During the first five months of 2026, battery storage discharge tripled compared with the same period in 2024. By absorbing excess midday solar output, stationary storage systems prevent severe over-generation curtailment and discharge stored clean energy directly into the evening net peak ramp when solar production wanes. This displacement of gas peaker turbines during the evening net peak hours represents a critical operational milestone for grid decarbonization.

Interregional Electricity Imports and Plant Retirements

Despite increasing generation from solar and batteries and a 7% increase in demand over this time period, there was a 19% decrease in net generation as electricity imports from nearby systems doubled in CAISO.

The doubling of electricity imports was driven by low-cost zero-carbon generation coming online across neighboring Western regions. Hydroelectric power imports from the Pacific Northwest increased as regional drought conditions subsided, while CAISO began importing from the new SunZia wind project in New Mexico starting April of this year.

Grid capacity also adjusted through thermal and equipment retirements. Generator retirements in CAISO between May 2024 and May 2025 totaled 555 MW and included a 300 MW battery installation that caught fire in January of 2025.

For commercial facility managers and residential homeowners evaluating solar panels in California, CAISO's transformation illustrates how utility-scale solar and battery storage are setting the operating standard for modern power networks.