Single Electricity Market (SEM)

Ireland; Northern Ireland. Status: operational.

Wholesale design: Integrated all-island energy market coupled to Europe, with centralized scheduling/dispatch and separate system-service procurement.

Market type
Jurisdictional market
Operators
EirGrid · SONI · SEMO
Dispatch model
central dispatch with mandatory gross-pool participation for dispatchable units
Where energy trades

Where does energy trade in Single Electricity Market (SEM)?

Energy in Single Electricity Market (SEM) trades in 5 layers: day-ahead, intraday, balancing, DS3 System Services and Capacity Remuneration Mechanism.

What a battery can sell

What ancillary services can a battery sell in Single Electricity Market (SEM)?

Single Electricity Market (SEM) has 14 ancillary-service products, across 7 families — fast frequency response, manual frequency restoration, contingency reserve, ramping reserve, replacement reserve, inertia & system strength and reactive power & voltage: Dynamic Reactive Response, Fast Frequency Response, Fast Post-Fault Active Power Recovery, Primary Operating Reserve, Ramping Margin 1, Ramping Margin 3, Ramping Margin 8, Replacement Reserve De-synchronised, and 6 more. 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.

Fast frequency response

  • Fast Frequency Response

    operational

    Deliver very fast active-power response after a frequency event.

    Direction
    upward or downward according to contract
    Trigger / range
    frequency event under DS3 performance methodology
    Eligibility
    qualified generating units, demand-side units, storage and other service providers meeting DS3 tests
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    regulated/tariff and contractual arrangements under the DS3 ruleset

    The 2-10 second interval is the product measurement window, not a stated maximum dispatch duration.

Manual frequency restoration

  • Tertiary Operating Reserve 1

    operational

    Provide the first slower layer of tertiary post-contingency reserve.

    Direction
    primarily upward response
    Trigger / range
    contingency/dispatch need
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    The 90-second to five-minute interval is a measurement window.

  • Tertiary Operating Reserve 2

    operational

    Provide longer post-contingency tertiary reserve and release faster products.

    Direction
    primarily upward response
    Trigger / range
    contingency/dispatch need
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    The five-to-20-minute interval is a measurement window.

Contingency reserve

  • Primary Operating Reserve

    operational

    Arrest frequency decline immediately after a contingency.

    Direction
    primarily upward response
    Trigger / range
    frequency event
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    The 5-15 second interval is a measurement window.

  • Secondary Operating Reserve

    operational

    Sustain and deepen post-contingency reserve after POR.

    Direction
    primarily upward response
    Trigger / range
    frequency event
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    The 15-90 second interval is a measurement window.

Ramping reserve

  • Ramping Margin 1

    operational

    Reward upward and downward ramp capability available over the next hour.

    Direction
    upward and downward
    Trigger / range
    forecast ramp and system need
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    One hour is the ramp horizon, not a fault-response deadline.

  • Ramping Margin 3

    operational

    Reward ramp capability over a three-hour horizon.

    Direction
    upward and downward
    Trigger / range
    forecast ramp and system need
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    Three hours is the ramp horizon.

  • Ramping Margin 8

    operational

    Reward ramp capability over an eight-hour horizon.

    Direction
    upward and downward
    Trigger / range
    forecast ramp and system need
    Eligibility
    DS3-qualified providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    Eight hours is the ramp horizon.

Replacement reserve

  • Replacement Reserve De-synchronised

    operational

    Provide replacement reserve from resources not synchronized at the event start.

    Direction
    upward
    Trigger / range
    TSO dispatch requirement
    Eligibility
    qualified de-synchronized providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    The cited sources do not give one unambiguous response time across RRD arrangements, so none is shown.

  • Replacement Reserve Synchronised

    operational

    Provide replacement reserve from units already synchronized after faster reserves are depleted.

    Direction
    upward
    Trigger / range
    TSO dispatch requirement
    Eligibility
    qualified synchronized providers
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    Twenty minutes to one hour is the DS3 performance interval, not a universal activation schedule.

Inertia & system strength

  • Synchronous Inertial Response

    operational

    Limit rate of change of frequency by rewarding synchronous inertia and available headroom.

    Direction
    frequency support
    Trigger / range
    instantaneous physical response to RoCoF
    Eligibility
    qualified synchronized units with measured inertia and reserve capability
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    SIR is not a dispatched MW product with a single response deadline.

Reactive power & voltage

  • Dynamic Reactive Response

    operational

    Provide rapid dynamic reactive current/power support during voltage disturbances.

    Direction
    reactive injection or absorption
    Trigger / range
    voltage disturbance under DS3 technical tests
    Eligibility
    qualified providers meeting dynamic reactive response tests
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    No single response time is published without the detailed test procedure.

  • Fast Post-Fault Active Power Recovery

    operational

    Restore active power rapidly after voltage recovery from a transmission fault.

    Direction
    active-power restoration
    Trigger / range
    after terminal voltage has recovered to at least 85% of nominal
    Eligibility
    qualified wind and other applicable nonsynchronous units meeting fault-recovery tests
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    The 250 ms criterion is measured after voltage recovery, not necessarily from fault inception; no response-duration value is inferred.

  • Steady State Reactive Power

    operational

    Maintain voltage by supplying or absorbing steady-state reactive power.

    Direction
    reactive power injection and absorption
    Trigger / range
    voltage-control instruction and capability curve
    Eligibility
    qualified providers meeting reactive capability tests
    Typical procurement
    Dynamic or not publicly stated
    Pricing
    DS3 tariff/contract rules

    Reactive power is normally measured in MVAr; MW procurement range is not applicable.

Getting paid to exist

Does Single Electricity Market (SEM) have a capacity mechanism?

Single Electricity Market (SEM) has 1 capacity/adequacy arrangement: SEM Capacity Remuneration Mechanism. The official sources do not say whether it is a central capacity market.

SEM Capacity Remuneration Mechanism

operational

Forward capacity auctions award de-rated capacity obligations; capacity providers face reliability-option difference payments when the reference price exceeds the strike price.

T-4 and supplementary T-1 auctions with locational constraints and auction price caps

Unit of obligation
provide capacity during scarcity and meet reliability-option/availability obligations
Auction held in 2025
Yes () — Dated from the day the auction ran.

DS3 System Services pay for operational capabilities and are separate from adequacy capacity.

EUR/MW-year in Ireland and GBP-equivalent settlement in Northern Ireland

Revenue routes

Merchant revenue routes

  • day-ahead and intraday energy
  • balancing energy
  • DS3 service payments
  • capacity payments
Where this comes from

Official sources

Rules

Service specification

Market 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 Single Electricity Market (SEM)

Who operates Single Electricity Market (SEM)?
Single Electricity Market (SEM) covers Ireland and Northern Ireland and is operated by EirGrid, SONI and SEMO.
Was a qualifying capacity event held in Single Electricity Market (SEM) in 2025?
Yes. SEM Capacity Remuneration Mechanism: a qualifying 2025 event is recorded (2025-05-22). Dated from the day the auction ran.
How is energy traded, priced and settled in Single Electricity Market (SEM)?
Single Electricity Market (SEM): Integrated all-island energy market coupled to Europe, with centralized scheduling/dispatch and separate system-service procurement. dispatch — central dispatch with mandatory gross-pool participation for dispatchable units.
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