IESO Board Market Rule Amendment Determinations
October 30, 2025
The IESO Board of Directors has approved the following market rule amendments:
- Capacity Auction Tie-Break Methodology (MR-00488-R00): The amendments introduce a multi-step tie-break process within the capacity auction clearing optimization. Effective Date: November 17, 2025.
- Post Go Live True-Ups for the Renewed Market (MR-00484-R00-R05): The amendments contain various non-substantive changes required to better align the market rules with the correct functioning of the renewed market’s implementation. Effective Date: December 3, 2025.
- 2025 Capacity Auction Enhancements (MR-00483-R00): The amendments will reduce the occurrence of unfulfilled commitments, resulting in improved capacity auction outcomes and improved reliability. Effective Date: November 17, 2025.
The amendment proposals, and the Board’s reasons for adopting the amendments, are available on the Proposed Market Rule Amendment webpage.