CAISO on April 16 sidelined a proposal to provide an additional market run for gas resources due to a lack of information on the subject and a need for operational experience with the ISO’s Extended Day-Ahead Market (EDAM).  

The proposed new market run, known as D+1.5, would occur between CAISO’s two-day-ahead market run, D+2, and day-ahead market run. D+1.5 would provide a better estimate of next-day markets as a potential to reduce reliability concerns, said NV Energy, a stakeholder in CAISO’s Gas Resource Management Working Group. 

Currently, CAISO uses two two-day-ahead market processes: D+2 and the residual unit commitment (RUC) look-ahead advisory. Stakeholders raised concerns about the RUC’s timing and forecasting accuracy and said there is a general “lack of confidence” using such information to inform fuel procurement decisions, per CAISO’s latest issue paper on the subject, published in January. 

D+1.5 could provide new information to participants that was not available in time for the D+2 but becomes available and accessible to CAISO. For example, scheduling coordinators could submit new or updated bids, informed by the next-day gas day trading activity, into the day-ahead market to inform the D+1.5, the paper says. 

However, to provide a D+1.5 market run, CAISO would need to establish a new process to collect gas trading data and run new forecasts. If not, D+1.5 would use the same forecasting information already used by the market processes on the trade day. Adding new forecasting services would increase vendor and personnel costs to monitor and maintain the new forecasting suite, the paper says.  

The “highest-priority scope item” for CAISO’s Gas Resource Management Working Group is to provide more market information to participants prior to the day-ahead market to support fuel procurement, the paper says. But the value of a new market run “must be weighed against the cost of gathering new information, running the optimization and validating a new stream of market results made available to market participants,” the paper says. 

“While we support the continued consideration of this new market run, we think it should be after we complete an assessment of D+2 and have some operational experience with EDAM and the new D+2 market run,” Sylvie Spewak, CAISO senior policy developer, said at the April 16 working group meeting. “At this time, we don’t intend on including the D+1.5 proposal in this upcoming straw proposal in detail. Let us know if you disagree with this approach.”