Executive Summary
The purpose of this report is to provide market participants a monthly summary of day-ahead and real-time markets performance for December, 2025. The key market performance highlights are presented here:
CAISO area performance:
Peak loads for ISO area increased a little in December compared to the previous month.
The cumulative frequency of prices in FMM above $250/MWh decreased from 0.0174 percent in November to 0 in December, while the cumulative frequency of negative prices increased from 1.31 percent in November to 2.23 percent in December, correlated with an increase in renewable generation curtailment. The cumulative frequency of prices in RTD above $250/MWh maintained at 0 from November to December, while the cumulative frequency of negative prices increased from 1.86 percent in November to 2.37 percent in December, correlated with a increase in renewable generation curtailment.
Average Day-Ahead, FMM and RTD DLAP prices in PGAE, SCE, SDGE, and VEA all decreased between from November to December.
The cumulative total congestion rent for interties increased from $0.2 million in November to $1.85 million in December. Majority of the congestion rents in November accrued on MALIN500_ISL(42,6%) and NOB_ITC(41.5%). Congestion rents on the MALIN500_ISL increased from $159,966 in November to $788,869 in December, while the congestion rent on IPPUTAH_ITC increased from $28,005 in November to $109,771 in December. Congestion rent of NOB_ITC increased from $11,883 in November to $768,920 in December.
Net Monthly Balancing Surplus in December was $3,534,324. The auction revenues credited to the balancing account for December were $5.39 million. As a result, the balancing account had a surplus of approximately $8.93 million compared to $6.46 million in the previous month, which was allocated to measured demand.
In December the monthly IFM average procurement increased for regulation up, non-spinning and spinning, while decreased for regulation-down reserves compared to the previous month. The monthly IFM average prices decreased for regulation up, regulation down, spinning and non-spinning reserves compared to the previous month. Day-ahead ancillary service prices remained volatile in December, similar to the previous month.
The total bid cost recovery increased from $9.73 million in November to $15.5 million in December. Out of the total monthly bid cost recovery payment for the three markets in December, the IFM market contributed 30.9 percent, RUC contributed 41.8 percent, and RTM contributed 27.3 percent of the total bid cost recovery payment.
RTIEO decreased from -$0.858 million in November to -$3.33 million in December. RTCO decreased from $11.0 million in November to $4.91 million in December.
The monthly exceptional dispatch uplift payments increased from $1,095,398 in November to $3,804,777 in December.
The number of market disruptions decreased from 35 in November to 8 in December. On Dec 16, there were 3 (2 RTD, 1 FMM) disruptions due to implementation of a market software patch.
The total volume of exceptional dispatch increased from 101,920 MWh in November to 156,988 MWh in December. There were spikes from Dec 24-26 due to planned transmission outage.
The curtailment of renewable energy increased a little in December compared to the previous month. Most curtailments continued to be solar.
Western Energy Imbalance Market (WEIM) performance:
The FMM ELAP prices in December decreased for all BAA. Besides, FMM ELAP prices were similarly volatile compared to the previous month.
The RTD ELAP prices in December decreased for all BAA. And RTD ELAP prices were similarly volatile compared to the previous month.
The cumulative frequency of FMM ELAP prices above $250/MWh decreased from 0.06 percent in November to 0.0428 in December. The cumulative frequency of negative FMM ELAP prices increased from 0.892 percent in November to 1.94 in December. The cumulative frequency of RTD ELAP prices above $250/MWh increased from 0.0463 percent in November to 0.0657 in December. The cumulative frequency of RTD ELAP negative prices increased from 1.4 percent in November to 2.16 percent in December.
Total WEIM RTIEO increased from $3.89 million in November to $5.68 million in December. Total WEIM RTCO increased from -$5.2 million in November to -$4.48 million in December.
Total WEIM BCR increased from $1.71 million in November to $1.82 million in December.
Total flexible ramping up uncertainty payment increased from $0.324 million in November to $0.439 million in December.
Total flexible ramping down uncertainty payment increased from $13248 in November to $18,955 in December.
Total forecast payment increased from $210,364 in November to $376,874 in December.
| Month | WEIM | FMM ELAP Prices | RTD ELAP Prices | Price Difference |
|---|---|---|---|---|
| 2025-12 | AVA | $30.03 | $30.47 | -$0.44 |
| 2025-12 | AVRN | $27.71 | $28.67 | -$0.96 |
| 2025-12 | AZPS | $29.16 | $30.82 | -$1.66 |
| 2025-12 | BANC | $36.48 | $37.15 | -$0.67 |
| 2025-12 | BCHA | $29.36 | $29.02 | $0.34 |
| 2025-12 | BPAT | $27.54 | $27.82 | -$0.28 |
| 2025-12 | EPE | $28.78 | $31.55 | -$2.77 |
| 2025-12 | IPCO | $30.05 | $30.86 | -$0.82 |
| 2025-12 | LADWP | $35.60 | $35.87 | -$0.27 |
| 2025-12 | NEVP | $29.57 | $31.50 | -$1.93 |
| 2025-12 | NWMT | $29.65 | $35.45 | -$5.80 |
| 2025-12 | PACE | $29.30 | $29.98 | -$0.68 |
| 2025-12 | PACW | $27.36 | $28.74 | -$1.38 |
| 2025-12 | PGE | $27.57 | $28.41 | -$0.84 |
| 2025-12 | PNM | $24.70 | $24.77 | -$0.06 |
| 2025-12 | PSEI | $28.11 | $28.19 | -$0.09 |
| 2025-12 | SCL | $28.75 | $28.95 | -$0.20 |
| 2025-12 | SRP | $29.20 | $30.00 | -$0.80 |
| 2025-12 | TEPC | $29.57 | $30.50 | -$0.93 |
| 2025-12 | TIDC | $36.49 | $37.17 | -$0.67 |
| 2025-12 | TPWR | $28.07 | $28.71 | -$0.64 |
| 2025-12 | WALC | $27.99 | $29.73 | -$1.74 |