Ontario Nuclear Supply

Provenance. This is IESO grid-operator market data, MW actually delivered to the Ontario grid, from the IESO Generator Output & Capability Report. The U.S. pages use NRC regulatory percent-of-rated-thermal-power. Different measurements, comparable for availability, never mixed: Ontario is never added into the U.S. national figure.

The Ontario forward curve is a different model from the U.S. one. It is not the U.S. projection extended north, and it should not be read as equivalent. CANDU units refuel on power, so the refueling-cycle signal the U.S. curve is built on does not exist in Ontario. This model holds announced refurbishments to their published return dates, excludes permanently retired units on a sourced basis, and samples the rest from the observed duration distribution back to 2019. It backtests at 80.6% P10 to P90 coverage against a nominal 80%, with individual windows ranging 67 to 93%. Two refurbishment return dates have settled so far and both came back about seven months early, so the spread around announced returns is a stated assumption rather than a fitted one, and it is revised as more of them settle.

No price-impact layer for Ontario. The $/MWh sensitivity model runs on EIA’s republished ICE hub feed, which carries no Ontario hub, nor SPP. (NYISO and ERCOT no longer belong on that list: both are now ingested directly from the ISO.) Ontario day-ahead zonal prices are stored, but Ontario is deliberately kept out of the price-sensitivity universe rather than given a modelled sensitivity it has not earned.