On July 10, 2025, several environmental groups filed suit against the Bonneville Power Administration (“BPA”) in the United States Circuit Court of Appeals for the Ninth Circuit (“Ninth Circuit”) over BPA’s announced plan to join the Southwest Power Pool’s (“SPP”) Markets+ rather than the California Independent System Operator’s (“CAISO”) Extended Day-Ahead Market (“EDAM”). Despite projections of nearly $65 million in annual savings from participating in EDAM, BPA cited concerns, such as market governance structure and long-term power and transmission rates, as driving factors in its final decision to join Markets+. The Ninth Circuit’s scope of review for this move boils down to whether BPA embodied “sound business principles” when electing to join Markets+, a standard that the court has historically used to grant BPA significant deference in its decision-making. Regardless, the case marks the latest in a growing history between these two RTO/ISOs as they compete to expand their market services beyond their traditional borders and grow their customer base across the western United States.
New Efforts to Expand Market Services
For Western stakeholders deciding whether to participate in voluntary markets that are not contingent on joining an RTO/ISO, two main options have recently emerged. The first is EDAM, CAISO’s planned day-ahead market slated to begin service in the spring of 2026. CAISO created EDAM to expand on the success of the Western Energy Imbalance Market (“WEIM”) platform—a system for non-CAISO members to participate in the CAISO’s real-time market—by enabling non-CAISO members to also participate in the CAISO’s day-ahead market. In return, all generation and load serving entities (“LSEs”) within a participating Balancing Authority Area (“BAA”) must either bid or self-schedule in the EDAM day-ahead market before these bids are subsequently re-optimized in the WEIM real-time market. CAISO designed the EDAM model to prioritize grid reliability while providing stakeholders substantial economic benefits and access to a more diverse and renewable-focused generation portfolio.
Conversely, SPP created Markets+ to enhance grid reliability by bundling both the real-time and day-ahead markets together into one system. SPP plans to eventually sunset its version of a voluntary real-time market, the Western Energy Imbalance Service Market (“WEIS”), and allow those participating in Markets+ to benefit from the same incentives. Like EDAM, the Markets+ model also places heavy emphasis on economic benefits, increased reliability, and its diverse generation portfolio. Unlike EDAM, however, all stakeholders’ supply and demand are optimized across the system by requiring participants, in part, to take all incremental market services from both the markets on the Markets+ system.
Navigating the Decision to Join the Markets
Over the last several years, the WEIM and WEIS imbalance markets competed for stakeholders to join their systems, and the recent creation of EDAM and Markets+ is quickly proving to be no different. As a result, entities that are considering whether to join one of these new day-ahead markets must scrutinize how each market’s unique characteristics will impact their partners and customers. BPA’s move to join Markets+ is a prime example of such an analysis, with BPA highlighting several key differences between the two markets that influenced its decision.
One such factor is the difference in governance structures between the two markets, with BPA in a press release describing the Markets+ governance structure as “superior” to EDAM despite the latter’s efforts to “incrementally improve its governance” and independence. EDAM is governed under the shared authority from Western Energy Markets (“WEM”) Governing Body and CAISO’s Board of Governors, the latter of which is appointed directly by the California Governor. Meanwhile, the governing SPP Markets+ Management Committee receives authority from the SPP Board of Directors, an entity elected by SPP’s member stakeholders.
The different approaches to congestion revenue allocation schemes were another significant consideration. EDAM recently approved a transitional change to its congestion revenue allocation policy, transitioning away from allocating all congestion revenue within a BAA where the transmission constraint originated to adequately account for rising prices for non-recipient participants caused by parallel flow. Markets+, on the other hand, allocates all congestion revenues directly to the constrained facility rights-holder. BPA preferred the Markets+ approach in its case, arguing that it was more successful in “promot[ing] transmission investments.”
Finally, each market has adopted unique resource adequacy requirements in attempts to bolster grid reliability. Markets+, for example, requires customers to participate in the Western Resource Adequacy Program (“WRAP”)—a regional effort addressing reliability challenges through planning and compliance of resource adequacy programs. BPA cited this approach as a more “uniform” model for mandating stakeholders to address resource adequacy challenges. Meanwhile, EDAM leaves the decision to the participant on whether to join a resource adequacy program such as WRAP, although EDAM stakeholders will be required to simultaneously participate in WEIM if they are not already doing so.
Despite BPA and other stakeholders’ reasoning for choosing Markets+, several other utilities have elected to join EDAM on different grounds. The most common justification given for this decision is the opportunity for higher benefits. The Public Service Company of New Mexico, for example, announced its plan to join EDAM starting in 2027, citing the nearly 250 percent higher potential annual benefits for participating in the market when compared to Markets+.
For further information or to discuss how DWGP may be of assistance with regards to navigating EDAM, Markets+, or any other energy market, please reach out to Sean Neal or Peter Scanlon.
Article By DWGP Summer Associate Griffin Krawitz – William & Mary School of Law, May 2026
