The California Community Choice Association (CalCCA) is asking the CPUC to set monthly planning reserve margins (PRMs) for 2028, with a higher margin in May and lower margins from July through September than under the annual and two-season methods Energy Division has used in its studies.
In a Nov. 2 filing, CalCCA estimated that its proposal could cut resource adequacy (RA) procurement costs by 4.0% to 5.7% relative to those methods while meeting the CPUC’s reliability standard of 0.1 expected shortfall events per year.
In August, CRI reported that neither Energy Division nor SCE found shortfalls in its projected 2028 baseline. Both had to stress their models to estimate the reserve margin.
CALCCA’S PROPOSAL
CalCCA proposes to set the margins using CAISO’s target monthly distribution of shortfall risk and Energy Division’s proposed import assumptions for 2028. The resulting reserve margins would be 16.9% in April, 27.4% in May and 10.7% to 14.6% from July through September.
CalCCA calculated a margin of 17.4% in each of those three summer months when it applied either of the methods used by staff to the same modeling case. Even with the lower margins, July through September would each require more than 52 GW of capacity because of higher peak demand. April and May would each require less than 44 GW.
CalCCA's proposed 2028 reserve margins
Higher in May, lower in July–September, with 80% of expected shortfall events in those three months
Source: CalCCA, Final 2028 PRM Study (Nov. 2, 2026, R.25-10-003), Attachment A, Tables 5, 7 and 8. CAISOTargetLOLE criteria, Case B. Peak demand derived from requirement and PRM.