2026 California ISO Summer Loads and Resources Assessment Report and Models posted

The California ISO has posted its 2026 Summer Loads and Resources Assessment Report and a Technical Appendix on the Seasonal assessments webpage. The ISO has also posted its PLEXOS stochastic production cost simulation model and multi-hour stack model used for the summer assessment. The files are also available on the Seasonal assessments webpage linked above.

The 2026 Summer Loads and Resource Assessment (Summer Assessment) evaluates expected 2026 summer supply and demand conditions for the ISO balancing authority area (BAA). The ISO publishes and shares results of the Summer Assessment each year with state regulatory agencies, industry participants, and stakeholders. This Summer Assessment fits into a broader collaborative effort on behalf of the ISO to prepare for summer system operations and maintain grid reliability.

The Summer Assessment shows continued improvement in resource availability particularly driven by accelerated resource development. This results in an increase in projected capacity margins that exceed demand and reserve requirements and have met performance target levels four years in a row. The ISO’s probabilistic assessment of the anticipated 2026 summer conditions indicates a surplus meeting the “one day every 10 year's loss-of-load expectation” (“1-in-10 LOLE”) planning target. The LOLE metric in this assessment measures the potential for calling on emergency measures, not actual loss of firm load.

These results do not take into account coincident extreme events such as those demonstrated in the last several years, including drought, wildfires and the continued potential for widespread regional heating events and other disruptions that can continue to pose reliability challenges for the ISO grid.

Please contact Sai Koppolu at skoppolu@caiso.com with any questions.