Nearly four months after the launch of Ontario’s nodal market, IESO officials say they are shifting from correcting implementation problems to seeking improvements to ensure the new model meets the goals of increasing market efficiency, transparency and competition.
“We’re getting … pretty close to what I would call more of a steady state … where we’ll be able to start to move from … addressing the day-to-day issues that come up for things that didn’t quite get implemented exactly as planned, to [looking at] the longer term,” Candice Trickey, director of Market Renewal Plan readiness, said in a briefing Aug. 21, the first in a promised quarterly series of updates. “How are things progressing? Are we seeing the things we wanted to see? … And where we aren’t, what do we need to [do to improve] that?”
The Renewed Market, which launched May 1, created a financially binding day-ahead market (DAM) and about 1,000 LMP nodes. (See Ontario Nodal Market Operating as Expected at 1-month Mark.)
Despite some implementation problems, IESO said the market has been working well, with prices strongly correlated to demand.
Data Points
Some data points as the market nears the four-month mark:
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- Nearly 30 traders have registered to transact in the virtual market, which allows them to submit hourly bids and offers in nine zones. Problems completing traders’ authorizations delayed the launch of the virtual market from May 8 to May 13. One large consumer has registered as a price-responsive load. Other organizations have begun the process of registering for the two new participation types.
- All required participants have registered reference levels under market power mitigation rules, with some refining their values based on their experience in the market. Reference levels include energy and operating reserve prices and resources’ energy ramp rates and lead times. The Market Power Mitigation Working Group has reduced its meeting frequency to monthly, with “no significant issues” identified.
- IESO said it has been issuing settlement statements and invoices within the required timelines, although increased processing times have resulted in invoices being issued later in the day than preferred by participants, an issue the ISO is working to address. The ISO created a Settlements Notifications webpage to advise participants of updates.
- Participant inquiries have increased under the new market. IESO said its Customer Relations unit has answered 80% of inquiries within two business days, although more complex questions have taken “much longer.” The ISO said 40% of market participants responded to its final market readiness survey, with nearly 90% saying IESO’s Customer Relations or Marketplace Training were “very” or “somewhat” effective. About 63% of respondents reported they generally are “comfortable operating,” and 35% said that “non-critical” operations still are incorporating changes. Only a few organizations reported they were “struggling to operate effectively,” IESO said.
‘Defects’
As expected, Notices of Disagreement have increased since the market launch. The ISO has confirmed its initial statements in two-thirds of cases and attributed one-third to defects that have been corrected. The grid operator is working through a backlog of disagreements.
Most of the defects affected small groups of participants, such as price responsive loads and resources eligible for generator offer guarantees — non-quick-start resources that commit to economically scheduled hourly generation commitments in advance of real-time (RT) dispatch.
But one defect, caused by a calculation error regarding residual uplifts, had a widespread effect. Although the two-settlement energy settlement amounts were calculated correctly, the day-ahead and real-time residual uplifts were calculated incorrectly and distributed to loads and exporters, resulting in adjustments to four uplift charge types. The ISO issued a notice Aug. 12 identifying the issue, the affected charge types and how resettlement will be completed.
Trickey said the rate of new defects in market systems has fallen from the first few weeks and that most were addressed with interim “workarounds” to avoid market effects.
One of the workarounds involved the five-minute interval Ontario Demand values reported in real time, which were overstated in some “limited circumstances.” IESO’s workaround “effectively adjusted forecast demand to largely mitigate this defect,” it said.
The ISO said some defects had no effect because workarounds were implemented, while others affected market outcomes briefly and required it to administer prices or correct schedules before settlement.
More complex defects required “extensive assessment” to determine if there was a material effect and could not be completed prior to settlement.
Thus far, the ISO said, two of those assessed had material effects necessitating the issuance of dispatch scheduling errors (DSEs): an incorrect calculation of the external congestion and net interchange scheduling limit price components for May 1-4; and an incorrect limit considered in the DAM for the ONT-PQAT interface on May 6. DSEs are issued when problems are discovered after settlements are issued; they allow the ISO to provide compensation to harmed parties but do not change prices.
Another five issues requiring extensive assessment are outstanding; the ISO said it likely will take another three to six months to determine whether these had material effects requiring DSEs.
Market Results
IESO officials said market results generally have been in line with expectations.
The market began during the “freshet,” the annual influx of water from spring rainfall and melting snow. Many hydropower projects must exit the operating reserve market and operate as “must-run” generators in spring because they have to flow the excess water through their turbines. (See Operating Reserve Prices Surge in Ontario.)
Summer brought its own challenges, Joseph Ricasio, a member of IESO’s control room team, said during the webinar. Hot weather sent the province’s demand soaring above its 2024 peak of 23,852 MW on seven occasions, with peaks as high as 24,862 MW. “I don’t remember the last time we received a lot of successive heat waves,” he said.
Between June 23 and 24, Ontario shifted from a net exporter during peak hours — as strong wind generation allowed it to ship energy to New York and Michigan — to a net importer as wind diminished.
It was a net importer on July 14-16 due to economic conditions and on July 27-29 as two large generators were “forced offline.”
“The generation and transmission performed very well this summer,” Ricasio said. “One advantage [of] being a net exporter is that it gives us a lever to address any adequacy concerns, and that’s because if it’s needed, we can curtail those exports.”
Despite the challenges, Ricasio said, the financially binding DAM has improved IESO’s ability to commit adequate generation for the next day. Some Level 1 Emergency Energy Alerts — a notice that all available generation resources are committed — have been identified based on day-ahead results, IESO said. “This gives advance notice to your neighbors that we may need their help,” Ricasio said.
‘Non-intuitive’ Results
Trickey said numerous participants have questioned “non-intuitive or unusual” market results. Some identified defects, while others were a result of the challenging summer temperatures and the new market’s multi-interval optimization.
“In an LMP market, the [offer] price is certainly an important determinant. But because we’re looking at optimizing over many, many intervals, [there can be] a difference in what the scheduling algorithm and the pricing algorithm are looking at,” she said. “So, you might see an offer close to the margin that appears uneconomic that gets scheduled.”
Director of Markets Darren Matsugu said the market had produced prices “reflective of system conditions and efficient resource schedules” with real-time and day-ahead prices converging when actual conditions matched forecasts, and diverging when there were deviations in real time due to large load forecast errors or unexpected outages. Although real-time prices were more volatile than day-ahead, more than 95% of load was met by day-ahead schedules, minimizing the price effect on consumers, the ISO said.
“Moving from the mild temperatures in May — where we saw … seasonally low demands and abundant supply — into what’s turned out to be a very hot summer, we’ve seen an associated increase in entry market prices, which is exactly what we would expect,” Matsugu said.
“We also observed higher natural gas prices over the summer, and as gas is often the marginal resource during these two periods, that also has upward pressure on market clearing prices,” he added.
Prices have consistently separated between the north, where bottled hydro supply can suppress prices, and the transmission-constrained south.
“This past May when demand was relatively low and we had substantial baseload generation available, we had very few intermediary peaking resources that were already online and available to increase output immediately,” he added. “But what we have seen is demand has increased over the summer, and more and more of those resources are being committed ahead of real time, either in day-ahead or in pre-dispatch. This increases the amount of incremental flexibility that can be dispatched on the system, if required.”
An average of 80 to 90% percent of non-quick start gas generators dispatched in real time — units that need one to six hours to start up and synchronize with the grid — were scheduled in the DAM over the first three months, providing grid operators and market participants “a clearer view and financial certainty for the next day’s operations while also leaving room to adjust to forecast uncertainty and outages in real time,” the ISO said.
Challenges in Scheduling of Pseudo Units
While the experience generally has been positive so far, “it isn’t perfect,” Ricasio said, citing IESO’s difficulties with pseudo unit (PSU) configurations, which model the mechanical interdependencies of combustion turbines and steam turbines.
Under the Renewed Market, PSU modelling is applied for DAM, pre-dispatch and RT timeframes for commitment, scheduling and dispatch.
IESO notified affected generators of workarounds to address the issues and said it is working on permanent fixes.
No Major Changes Expected
Matsugu said the market thus far has worked as designed to reduce out-of-market payments and increase efficiency.
“I do expect that over time, there’ll be some fine tuning that may be eventually required on these things, as is to be expected with any market — and particularly given the significance of the change that we’ve introduced with Market Renewal,” he said. “But at this point, there are no major design issues that require immediate fixes, just something that we’ll continue to pay close attention to.”
Matsugu cautioned that IESO had only two seasons of experience with the new market rules, saying it will gain valuable knowledge in the coming fall and winter.
“It is premature, I think, to draw too much based upon the still very short time frame that we’ve been operating,” he said. “We are still working toward … a steady state, where we can see the market performance under a diverse set of outcomes and conditions. [And] the participants themselves are still establishing their own competitive bid and offer strategies.”
Participants’ Questions
ISO officials answered several questions from stakeholders during the Aug. 21 presentation. Aaron Lampe, of Workbench Energy, asked about the effect of the market on pre-dispatch prices.
Matsugu said comparing PD prices before and after May 1 is “really comparing apples to oranges [because] in pre-market, our pre-dispatch was doing a one-hour optimization and not looking out across the balance of the day.”
“The only thing in common between pre-market pre-dispatch and our current pre-dispatch is really just what it’s called,” he added.
Rob Coulbeck, of Red Jar Energy Partners, said the ISO’s pre-dispatch three-hour look ahead was restrictive and asked if it could add another hour for import and export transactions that don’t clear in the DAM.
“I think that probably falls in the bucket of future design enhancements,” responded Matsugu. “There’s probably a whole bunch of different things that we can start to consider once we’re satisfied that the current market is performing.”










