CAISO has dismissed Powerex’s contention that the ISO only recently has “revealed” that participation in its Extended Day-Ahead Market is voluntary at the balancing authority level but not voluntary for “individual customers” operating within the BA participating in the market.
“Powerex’s claim is incorrect and directly at odds with the factual record,” CAISO wrote in a June 17 “limited answer” filed in the FERC docket for PacifiCorp’s proposed revisions to its Open Access Transmission Tariff, intended to facilitate the utility’s participation in EDAM (ER25-951).
In February, PacifiCorp’s OATT proceeding had opened yet another front in the competition between EDAM and SPP’s Markets+.
That’s when Powerex — a strong Markets+ backer — published a paper arguing that PacifiCorp’s revisions showed the EDAM contained a “design flaw” in how it allocates transmission congestion revenues in situations when congestion results from loop flow. (See Powerex Paper Sparks Dispute over EDAM ‘Design Flaw’.)
CAISO and PacifiCorp initially rebuffed that characterization, but the ISO and its stakeholders did move to quickly address the matter with congestion revenue allocation rule changes developed through an expedited stakeholder process. (See CAISO Approves New EDAM Congestion Revenue Allocation Design.)
But the issue spelled out in CAISO’s June 17 answer represents a new twist in the running dispute in the OATT proceeding.
In its answer, CAISO was responding to a June 11 comment Powerex submitted in the docket in which the Vancouver, B.C.-based power trader said the ISO has long promoted the EDAM as “voluntary and incremental” — a “natural evolution” of the Western Energy Imbalance Market (WEIM).
But, Powerex went on to contend, in a May 19 filing, CAISO for the first time “revealed” a “radically different approach” in which “EDAM could no longer be described as voluntary at all because only PacifiCorp (or other prospective balancing authorities) will be offered the choice to participate in EDAM.”
Powerex was pointing specifically to CAISO’s statements around an EDAM provision that allows a participating BA to “carve out” the embedded transmission of nonparticipating transmission service provider (TSP) from EDAM’s market optimization. In the May 19 filing, the ISO said it agreed PacifiCorp had the right to take that action but added that “any such carveouts should be an option of last resort.”
Instead, CAISO argued, a “similar and more efficient” option would be for the nonparticipating TSP to self-schedule the use of its own transmission within EDAM and directly settle the associated energy schedules, including congestion price differences, with the market operator.”
Powerex said this showed CAISO was seeking to “achieve this compulsory participation” and create a “captive market” along the lines of an RTO, but without providing the full benefits of an RTO.
That would mean PacifiCorp’s decision to join the market would “in turn, require every electricity transaction and every delivery by every customer in PacifiCorp’s area to take place through EDAM,” Powerex wrote. “In addition, once PacifiCorp joins EDAM, all of its own transactions and all of its own deliveries will also be required to occur entirely through EDAM.”
Powerex went on to warn that “if CAISO’s new vision for EDAM is accepted, it would effectively make all activity in the electricity sectors of Wyoming and Utah, as well as significant portions of Idaho, Oregon and Washington, captive to CAISO’s authority and ongoing decision-making under CAISO’s governance structure, as a result of PacifiCorp’s election to join EDAM.”
‘No Recognizable Reason’
In its June 17 answer, CAISO retorted that, although Powerex “professes surprise” at the ISO’s statements in its May 19 filing, those comments represented “nothing new, surprising or radically different” from the ISO’s previous description of EDAM.
“In fact, … CAISO was explicit in its 2023 tariff amendment filing to implement the EDAM design — on which Powerex submitted comments not even raising this subject — that participation in EDAM is voluntary at the balancing authority level but that all supply and demand in each EDAM balancing area must participate in the day-ahead market,” the ISO wrote.
CAISO noted FERC approved this “foundational concept” of the EDAM in its December 2023 order approving the market’s tariff and “should reject Powerex’s factually inaccurate claims and its arguments based on those claims.”
It pointed out that the transmittal letter accompanying the EDAM tariff filing stated the tariff included three options for the use of OATT transmission service rights in the market but that CAISO “had rejected proposals for other options involving broad or automatic opt-outs or carveouts of transmission capacity from the market.”
The transmittal letter noted that CAISO and its stakeholders had determined that carveouts would create market inefficiencies, in part by potentially creating congestion in situations when a carveout leaves a path underused despite the availability of sufficient transmission capacity.
“In addition, Powerex contradicts history in claiming the CAISO is in 2025 announcing a ‘radically different approach’ under which every electricity transaction and every delivery by every customer in PacifiCorp’s area will take place through EDAM. The CAISO made this requirement clear multiple times in its 2023 filing of tariff amendments to implement EDAM,” the ISO wrote.
“In short, there is no cognizable reason for surprise on Powerex’s part,” it said.
