IESO

Ontario, Canada.

Wholesale design: locational day-ahead and real-time energy markets with co-optimized real-time operating reserve, contracted ancillary services, and an annual seasonal capacity auction.

Operator
Independent Electricity System Operator
Nominal frequency
60 Hz
Where energy trades

Where does energy trade in IESO?

Energy in IESO trades in 2 layers: Day-Ahead Market and Real-Time Energy and Operating Reserve Markets. Participation in Real-Time Energy and Operating Reserve Markets is mandatory. Scheduling and settlement, where the official sources state them, are in the table below.

Layer Scheduling Settlement
Day-Ahead Market hourly schedules with the renewed-market calculation and settlement framework financially binding day-ahead locational prices
Real-Time Energy and Operating Reserve Markets (mandatory) five-minute schedules and prices real-time locational energy prices and uniform clearing price for each operating-reserve class, subject to market rules
What a battery can sell

What ancillary services can a battery sell in IESO?

IESO has 7 ancillary-service products, across 5 families — regulation, contingency reserve, operating reserve, reactive power & voltage and black start & restoration: 10-Minute Non-Synchronized Reserve, 10-Minute Synchronized Reserve, 30-Minute Reserve, Certified Black Start Facility Service, Regulation Service, Reliability Must-Run Service, Reactive Support and Voltage Control Service. Response timing, direction and eligibility for each are in the cards below, as the official sources state them.

Facts below are stated as the official sources state them. A missing line means the source does not state that value — never that the value is zero.

Regulation

  • Regulation Service

    Match total generation and load moment to moment and correct frequency variations.

    Activation
    automatic control signal
    Trigger / range
    continuous symmetric scheduled range around the resource operating point
    Pricing
    contract-specific

Contingency reserve

  • 10-Minute Non-Synchronized Reserve

    Provide qualified non-synchronized standby energy or demand reduction after an unexpected system event.

    Activation
    IESO dispatch instruction
    Expected within
    10 minutes
    Sustain
    at least 1 h
    Trigger / range
    dispatchable capability available within ten minutes; higher-quality synchronized reserve may satisfy this requirement through the reserve hierarchy
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    five-minute class market-clearing price; energy payment if activated

  • 10-Minute Synchronized Reserve

    Provide synchronized standby energy or demand reduction after an unexpected system event.

    Activation
    IESO dispatch instruction
    Expected within
    10 minutes
    Sustain
    at least 1 h
    Trigger / range
    synchronized dispatchable capability; the overall OR requirement covers the largest contingency plus half of the second-largest contingency
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    five-minute class market-clearing price; energy payment if activated

  • 30-Minute Reserve

    Provide additional non-synchronized standby energy or demand reduction within thirty minutes.

    Activation
    IESO dispatch instruction
    Expected within
    30 minutes
    Sustain
    at least 1 h
    Trigger / range
    dispatchable capability available within thirty minutes; ten-minute reserve classes can also satisfy the thirty-minute requirement through the product hierarchy
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    five-minute class market-clearing price; energy payment if activated

Operating reserve

  • Reliability Must-Run Service

    Require location-specific energy or operating-reserve offers when needed to maintain grid reliability.

    Activation
    contract terms and IESO instruction
    Trigger / range
    facility- and local-reliability-specific
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    contract-specific

Reactive power & voltage

  • Reactive Support and Voltage Control Service

    Maintain acceptable localized reactive-power and voltage levels on the IESO-controlled grid.

    Activation
    automatic voltage control and IESO instruction
    Trigger / range
    prevailing system conditions and facility-specific reactive capability
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    contract-specific

Black start & restoration

  • Certified Black Start Facility Service

    Restart generation without an external power source and support restoration after a blackout.

    Activation
    IESO restoration instruction
    Trigger / range
    facility-specific certification and restoration plan
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    contract-specific
Getting paid to exist

Does IESO have a capacity mechanism?

Yes — IESO Capacity Auction is a central capacity market.

IESO Capacity Auction

The auction is the short-term balancing component of Ontario's broader resource-adequacy framework. Existing, non-committed demand response, generation, storage, and qualified imports may participate.

Unit of obligation
MW of cleared capacity obligation with availability requirements during specified business-day windows
Auction held in 2025
Yes () — Dated from the opening of the bidding window.
Where this comes from

Official sources

Rules

Service specification

Market explainer

Capacity-mechanism explainer

Capacity result

Current as of · from the Global Electricity Market Catalogue v1.2.0 (compiled to , CC BY 4.0). Facts belong to the linked official authorities; verify the current rules before design or bidding decisions.

Questions

Common questions about IESO

Who operates IESO?
Independent Electricity System Operator operates IESO, covering Ontario, Canada.
Was a qualifying capacity event held in IESO in 2025?
Yes. IESO Capacity Auction: a qualifying 2025 event is recorded (2025-11-26). Dated from the opening of the bidding window.
How is energy traded, priced and settled in IESO?
IESO: locational day-ahead and real-time energy markets with co-optimized real-time operating reserve, contracted ancillary services, and an annual seasonal capacity auction.
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