Ontario Demand
Ontario Demand reached 24,789 MW on August 11, HE 18 – marking the second highest peak demand of 2025. The highest peak demand for 2025 continues to be 73 MW higher at 24,862 MW and occurred at the end-of-June heat wave.
Weekly Day-Ahead and Real-Time Price Trends by Components and by Zone
Day-Ahead (DA) and Real-Time (RT) zonal prices increased compared to the previous week. DA zonal prices ranged from $90/MWh (Niagara) to $101/MWh (Ottawa), while RT zonal prices ranged between $64/MWh (Northwest) to $88/MWh (Ottawa). In both the Northeast and Northwest zones, congestion and losses increased in RT compared to DA.
The DA and RT price by zone and by component for the past week is shown below.
Day-Ahead and Real-Time Prices
Looking at last week’s day-ahead and real-time hourly prices, the day-ahead OZP was more than $98/MWh, while the real-time OZP was $84/MWh. There were 9 real-time hourly OZP spikes greater than $200/MWh, with the highest price hitting $505.08/MWh (on August 11). The peak Ontario Demand last week was 24,789 MW (on August 11, HE 18). The peak demand on August 11 – when OZP hit its highest level – was 24,500 MW at HE 17. Three consecutive price spikes in HE 17 to HE 19 occurred on August 10.
OR Prices
Both real-time and day-ahead Operating Reserve (OR) prices remain elevated compared to historical averages. The average weekly day-ahead 10S price was $21.44/MW, while it was lower at $18.55/MW in real-time. The most notable trend last week is the very high real-time 10S price spike of $470.89/MWh (coincident with the real-time OZP spike last week). As noted in multiple of our weekly reviews, the OR market supply stack is now tighter than under the legacy market and this has likely been the primary driver of higher OR prices.
Day-ahead OR prices closely tracked the trend in energy prices. The highest day-ahead OR price was $213.01/MWh which occurred on August 12, HE 18. For reference, the day-ahead energy price was $243.19/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 with the exception of a few OR price spikes at the same time as high energy prices.
Zonal Prices and Congestion
Last week, the Niagara zone saw more frequent hours of negative congestion, while both the Ottawa and East zone saw positive congestion. Similar to most other weeks since the renewed market launched, the Northwest and Northeast zones saw negative congestion in the day-ahead timeframe. The Northeast zone’s congestion was very minor and the Northwest zone’s congestion reached a low of -$21.52/MWh. For the Niagara zone, several hours of negative congestion were concentrated on August15 and August 16. Positive congestion was observed in Ottawa and in the East zone on August 17, HE 14 and HE 15.
Real-time zonal prices in the Northwest and Northeast remain volatile – with the Northwest seeing some swings from negative to positive congestion. The main negative congestion for the Northwest occurred on August 11, August 12 and August 15. The Northeast zone saw negative congestion also on August 11 and August 12 but not to the same degree as the Northwest zone. The lowest congestion was -$445.19/MWh for the Northwest zone on August 11, HE 17 (coincident with the highest real-time OZP spike). Essentially, both the Northeast and Northwest zones are seeing materially lower prices close to or during the highest OZP hours.
Like the week prior, the Ottawa and East zone experienced positive real-time congestion again (note that the East zone was not included in the figure in the previous week’s review). Also, similar to the prior week, the positive congestion in the Ottawa zone was coincident with the positive congestion seen in the East zone. The most positive congestion occurred on August 17, HE 11 to HE 14 and hit $93.04/MWh and $28.73/MWh for the Ottawa and East zone respectively. The Niagara zone saw several hours of extreme negative congestion, concentrated on August 15 with a low of -$324.88/MWh. The West zone saw a few hours negative congestion last week, with congestion hitting a low of -$59.27/MWh (on August 13, HE 21). There was also congestion in the Southwest zone with high of $13.68/MWh and a low of -$2.15/MWh.
