IESO Quarterly Reliability Outlook, June 2025
June 25, 2025
In addition to the Reliability Outlook and associated data tables and methodology, the IESO has made its Transfer Capability Assessment Methodology for the Near-Term Transmission Planning Horizon publicly available. The Ontario Transmission System document was consolidated with this Transfer Capability Assessment Methodology document. Operating Limits previously documented in the Ontario Transmission System document are now available in the Reliability Outlook Tables.
“Electricity demand is projected to grow modestly, with firm demand expected to rise by 1% in 2025 and 2.7% in 2026. The outlook reflects lower demand projections compared with previous forecasts due to evolving economic conditions, including slower growth from data centres and electric vehicle manufacturing facilities. Long-term growth is expected to remain strong,” IESO said via LinkedIn.
“This will also be the first summer season following the launch of the renewed market on May 1, 2025, which introduced a Day-Ahead Market that commits resources the day before real-time through financially binding schedules, increasing operational and price certainty.”
Recent IESO Actions to Improve Efficiency:
- New battery storage projects procured through the Expedited Long-Term (E-LT1) RFP are expected to connect to the grid throughout the Outlook period, while the Oneida Energy Storage Project recently achieved commercial operation in Q2 2025.
- Approximately 2,100 MW was cleared in last year’s Capacity Auction for summer 2025.
- Upgraded capacity resources procured via the Same Technology Upgrades Solicitation, which are expected to come online throughout this year.
- Approximately 250,000 smart thermostats that are enrolled in the Save on Energy Peak Perks demand response program, which reduces peak demand on hot summer days. Current participants – which consist of residences and, new this year, small businesses – can deliver a demand reduction of about 200 MW.
The IESO issues its Reliability Outlook each quarter. Here is the most recent issue and related documents.
From July 2025 – December 2026
- Reliability Outlook Report (Released June 19, 2025)
- Reliability Outlook Tables (Released June 19, 2025)
- Methodology to Perform the Reliability Outlook contains information regarding the methodology used to perform the demand forecast, resource adequacy assessments, and transmission adequacy assessments in this Outlook report.
- Transfer Capability Assessment Methodology documents the methodology used for performing assessments of Transfer Capability of the Ontario Bulk Electric System (BES) for transmission planning studies. This methodology is in accordance with the North American Electric Reliability Corporation (NERC) standard FAC-013-2. The IESO has also utilized this methodology for the transmission assessment beyond the first 18 months in the Reliability Outlook.
Previous Reliability Outlook Reports and related information can be found in the Document Library, under the Planning and Forecasts category.
