CAISO‘s Department of Market Monitoring has asked the ISO to re-evaluate its intertie scheduling proposal for the Extended Day-Ahead Market because of potential impacts on market participants.

CAISO held an impromptu workshop Nov. 14 to address outstanding stakeholder questions and concerns about the proposal after receiving the DMM’s comments, which urged the ISO to use an alternative for EDAM’s go-live in 2026. (See EDAM Intertie Scheduling Processes Raise Stakeholder Concerns.)

A primary issue is that in CAISO’s existing market, intertie schedules are at a scheduling point (SP). However, a generation facility or load is not exactly at its assigned SP node, and this discrepancy affects congestion management, pricing and settlements, DMM noted in its comments.

CAISO tried to solve this problem by modeling intertie injections and withdrawals at one of several generation aggregation points (GAPs). Each GAP would have its own congestion and loss prices, so the prices of imports and exports at the same intertie would be different for schedules associated with different GAPs, DMM said. This new approach will create multiple prices for the same intertie and will affect market participants with transactions at EDAM and bilateral market interties, DMM said.

“It seems clear to DMM … that market participants are concerned that these changes could negatively impact their business operations and practices, or at the very least they have not had adequate preparation to consider the potential impacts,” DMM said in its comments.

The GAP intertie proposal could cause market participants to be left without knowing which GAP combination will be used for their day-ahead pricing. The GAP approach also could result in a market with multiple prices for the same intertie, meaning imports could clear at higher offer prices than other imports that are offered at lower prices, DMM said.

DMM recommended CAISO either keep the current SP approach or assign each intertie to a single generic GAP until stakeholders have the chance to go through the proposal in the ISO’s policy revision process.

At the Nov. 14 workshop, CAISO staff said the ISO realizes there are a lot of questions and concerns about “how fast we are moving” and that the grid operator is working on implementing a transitional period for the EDAM GAP intertie approach.

“We are interested in making sure everyone is ready for whenever we make these changes in our market’s design,” said George Angelidis, executive principal at CAISO. “We would like to actually work with you and work on a transition plan that would [take] us through the journey together to maintain the timing of EDAM in May 2026.”

CAISO is developing a transitional period for implementing certain intertie scheduling processes, including continuing to use SPs at CAISO interties for scheduling, mirroring and scheduling distribution, among other functions. At non-CAISO EDAM interties, the transitional period would include using a single GAP for scheduling, schedule distribution and locational marginal pricing calculations.

Resource adequacy import processes will be “simplified” during the EDAM transitional period, Angelidis said. RA monthly showings will occur at a CAISO SP tie, which is the same process used today in the ISO’s market. The process for reassigning RA obligations will stay the same in EDAM during the transitional period, specifically for those that are not reassigned in a WEIM or non-WEIM BAA.

CAISO has not designated a concrete time frame for the transitional period, an ISO spokesperson told RTO Insider in an Nov. 17 email. Before transitioning to the FERC-approved intertie scheduling model, the ISO would have extensive discussions with stakeholders to determine the timeline and ensure alignment, the spokesperson said.