Summary of the CPUC’s Recent LOLE Workshop

On September 15, 2026, the California Public Utilities Commission (“CPUC”) held a workshop on the results of the agency’s Energy Division (“ED”) Draft 2028 Resource Adequacy (“RA”) Loss of Load Expectation (“LOLE”) Study.  The RA program policy framework was first adopted in 2004 by the CPUC to ensure electric service reliability in California.  CPUC-jurisdictional load serving entities (“LSEs”), companies or organizations which buy electric power on the wholesale market to sell or deliver to end-use customers, must meet the established RA obligations.  The program guides capacity resource procurement and infrastructure investment to ensure that the capacity to deliver reliable electricity is available where and when it is needed.  The current CPUC RA proceeding can be found here.  Both resource suppliers and LSEs must also meet the California Independent System Operator’s (“CAISO’s”) RA program rules with respect to specifying supplies that are scheduled or made available for dispatch across the transmission system.

The CPUC’s LOLE Study Process and Results

The CPUC uses the LOLE Study to measure the reliability of the power system by determining how much generating capacity must be available to avoid electricity shortages that could compromise the integrity of the state-wide grid.  The California system utilizes a target 0.1 LOLE, which means that the modeling system plans for a major disruptive event to occur once every ten years.  Thus, the LOLE study is crucial for ensuring the reliability modeling encompasses the resources available for an average day and for a day which features a high-stress or contingency event to the state’s electricity system.

The workshop presented updated results to past modeling, as well as additional studied scenarios, corrections to the Planning Reserve Margin (“PRM”) calibration tool, updates to the Inputs and Assumptions which underlie the determination, and modifications to the base case scenario.

After running its own modeling, the ED’s study found a 21% PRM to be effective for peak months, and a 19% PRM in non-peak months.  These results are relatively consistent with previous years’ PRMs.  Utilizing the CAISO’s recently updated resource fleet listing, the study’s results demonstrated that the system is over-reliable by about 5 or 6 gigawatts (“GW”) of effective capacity.  ED determined that adding a flat load of about 6 GW achieves a 0.1 LOLE, or a scenario planning for an electricity shortfall expected to happen on one day every ten years.  Further, ED found that tightening the CAISO’s simultaneous import limit to 0 GW still results in a 0.1 LOLE, and that a 95% capacity prorate of about 5.7 GWs has the same effect.

The draft LOLE study performed by ED also aligned the Unforced Capacity (“UCAP”) framework to align with the LOLE modeling.  Track 2 of the current RA proceeding is expected to resolve UCAP implementation, which would allow the CAISO to eliminate forced outage substitution rules deemed ineffective and overcomplicated, and would allow the PRM to serve as a more targeted tool for catastrophic loss of capacity events.

Following the ED’s study results, Southern California Edison (“SCE”) also presented results of their 2028 LOLE study, which demonstrated a resource portfolio calibrated to meet or exceed the 0.1 LOLE.  SCE framed their results as an examination of how many resources are needed for the forecast load, and to examine the amount of added load blocks which could serve extra load, arguing that the latter amount should be equivalent to the RA requirements for 2028. California Community Choice Association (“CalCCA”), which works on behalf of community choice aggregators serving specific communities in California, also presented their own 2028 LOLE study.  Employing a risk-reserve model similar to ED’s flat load scenario, CalCCA argued that the challenges of a single annual PRM would be well abated by instead adopting a month-to-month PRM.

What’s Next?

ED’s final 2028 LOLE study report, which will include stress tests and a final PRM recommendation for the 2028-2029 RA compliance years, is expected to be issued October 13.  In the interim, staff will further investigate the Prorated Scenario methodology, as well as SCE’s prorate modeling results, which will be incorporated in the October Final Report.

For more information, contact Andy Brown or Clarissa Maloney.