Blocked Dispatches by the IESO Remain Elevated in August (Dispatch Deviation Report)
The IESO has released the Dispatch Deviation report for August. Although the market interventions have decreased from the high set in July, they remain elevated as compared with August 2024. There were 10,516 blocked and one-time dispatches for the month, averaging 1.2 IESO interventions to the dispatch algorithm every 5 minutes (noting 5-minute intervals can experience multiple interventions). Compared to August 2024, August 2025 has recorded 2.7 times more total interventions (blocked and one-time dispatches).
Day-Ahead and Real-Time Price Trends by Components and by Zone
Day-Ahead (DA) and Real-Time (RT) zonal prices in the last two weeks increased compared to the previous three weeks. DA zonal prices ranged from $43/MWh (Niagara) to $49/MWh (Northwest), while RT zonal prices ranged between $37/MWh (Niagara) to $45/MWh (Northwest). Prices overall in the IESO-Administered Market (IAM) have declined significantly from August.
The DA and RT price by zone and by component for the past two weeks are shown below.
Day-Ahead and Real-Time Prices
For the last two weeks, the average hourly day-ahead OZP was $46.73/MWh, while the real-time OZP was $40.24/MWh. There were two real-time hourly OZP spikes greater than $200/MWh, with the two highest prices hitting $294.25/MWh (on September 20, HE 17) and $259.04/MWh (on September 21, HE 13). The high price spike on a Sunday (September 21) is due to a rise in gas supply to meet a demand increase of 568 MW from the previous hour and an increase in exports to Michigan and Minnesota of 105 MW from the previous hour. The peak Ontario Demand last week was 19,931 MW (on September 18, HE 17). The peak demand on September 20 – when OZP hit its highest level – was 16,005 MW at HE 17.
OR Prices
Last week, there were a couple of real-time Operating Reserve (OR) price spikes. The average weekly day-ahead 10S price was $10.79/MW, while it was lower at $5.19/MW in real-time. The most notable trend last week is the two very high real-time 10S price spikes of $210.68/MWh and $159.01/MWh (coincident with the highest real-time OZP spikes last week).
The highest day-ahead OR price was $77.66/MWh which occurred on September 15, HE 18. For reference, the day-ahead energy price was $109.31/MWh at this time.
Real-time OR prices were low (i.e., near $0/MWh) for several hours of the week with OR prices exhibiting less volatility compared to energy prices. As mentioned previously, there were a few high real-time OR prices towards the end of last week coincident with real time OZP spikes. The highest real-time OR price was $210.68/MWh on September 20, HE 17.
Zonal Prices and Congestion
For the last two weeks, congestion was high in the Northwest and West zones in the day-ahead time frame. The Niagara zone saw some hours of minor congestion. Several hours of congestion for the Northwest zone was concentrated on September 16 swinging from positive to negative congestion from the early morning to evening hours. There were also several hours of negative congestion concentrated in the late evening and nighttime of September 13. Congestion in the Northwest zone reached a high of $19.37/MWh on September 16, HE 3 while it reached a low of -$1.32/MWh on September 13, HE 19. There was only negative congestion for the West zone on September 8 and September 10 with a low of -$20.51/MWh (as mentioned in last week’s MRP Review). The Niagara zone saw minor congestion but in consecutive hours across the last two weeks. Congestion in the Niagara zone reached a low of -$3.93/MWh.
Real-time zonal prices in the Northwest zone remain volatile – with the Northwest seeing frequent hours of positive congestion, especially in the last week. The peak positive congestion observed for the Northwest zone was $296.19/MWh on September 8, HE 19. Congestion in the Northwest zone reached a low of -$44.26/MWh on September 16, HE 17. The Northeast zone saw minor negative congestion. The Northeast zone observed congestion with a low of -$1.87/MWh.
In real time, similar to the day-ahead time frame, the Niagara and West zone observed negative congestion. The negative congestion in the Niagara zone was minor reaching a low of -$3.02/MWh. The West zone observed a few hours of negative congestion mainly on September 8 and September 10 reaching a low of -$19.83/MWh on September 8, HE 18.
