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 table below; a product's full record lists the official sources behind it.

Every value below comes from the official sources listed in that product's full record. Most products cite more than one, and the published sources do not say which of them states each individual value, so the binding is to the product's record rather than to a single document. A missing line means the source does not state that value — never that the value is zero.

Scroll the table sideways for the rest of the columns →

14 ancillary-service products in Single Electricity Market (SEM), grouped into 7 families. Each row runs left to right through one product's life: how it activates, how quickly it has to respond, how long it has to keep delivering, and how it is bought.
Service How it activates Response Sustained delivery Procurement
Fast frequency response
Fast Frequency Response FFR upward or downward according to contract operational Response type automatic post-fault response Trigger frequency event under DS3 performance methodology Bought DS3 System Services contracts How it settles availability/performance-based DS3 service payment Pricing design regulated/tariff and contractual arrangements under the DS3 ruleset
Full record for Fast Frequency Response — page or table locator recorded
What it is for

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

Published checkpoints

Measurement window: 2 s to 10 s

Who can provide it

qualified generating units, demand-side units, storage and other service providers meeting DS3 tests

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Manual frequency restoration
Tertiary Operating Reserve 1 TOR1 primarily upward response operational Response type automatic or dispatched reserve response Trigger contingency/dispatch need Bought DS3 System Services contracts How it settles availability/performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Tertiary Operating Reserve 1 — a topic in the document is named, but not a page or table
What it is for

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

Published checkpoints

Measurement window: 90 s to 5 min

Who can provide it

DS3-qualified providers

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Tertiary Operating Reserve 2 TOR2 primarily upward response operational Response type dispatched reserve response Trigger contingency/dispatch need Bought DS3 System Services contracts How it settles availability/performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Tertiary Operating Reserve 2 — a topic in the document is named, but not a page or table
What it is for

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

Published checkpoints

Measurement window: 5 min to 20 min

Who can provide it

DS3-qualified providers

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Contingency reserve
Primary Operating Reserve POR primarily upward response operational Response type automatic post-fault reserve Trigger frequency event Bought DS3 System Services contracts How it settles availability/performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Primary Operating Reserve — a topic in the document is named, but not a page or table
What it is for

Arrest frequency decline immediately after a contingency.

Published checkpoints

Measurement window: 5 s to 15 s

Who can provide it

DS3-qualified providers

Notes from the source

The 5-15 second interval is a measurement window.

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Secondary Operating Reserve SOR primarily upward response operational Response type automatic/post-fault reserve response Trigger frequency event Bought DS3 System Services contracts How it settles availability/performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Secondary Operating Reserve — a topic in the document is named, but not a page or table
What it is for

Sustain and deepen post-contingency reserve after POR.

Published checkpoints

Measurement window: 15 s to 90 s

Who can provide it

DS3-qualified providers

Notes from the source

The 15-90 second interval is a measurement window.

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Ramping reserve
Ramping Margin 1 RM1 upward and downward operational Response type scheduled ramping capability Trigger forecast ramp and system need Bought DS3 System Services contracts How it settles capability/performance service payment Pricing design DS3 tariff/contract rules
Full record for Ramping Margin 1 — a topic in the document is named, but not a page or table
What it is for

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

Published checkpoints

Ramp horizon: 1 h

Who can provide it

DS3-qualified providers

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Ramping Margin 3 RM3 upward and downward operational Response type scheduled ramping capability Trigger forecast ramp and system need Bought DS3 System Services contracts How it settles capability/performance service payment Pricing design DS3 tariff/contract rules
Full record for Ramping Margin 3 — a topic in the document is named, but not a page or table
What it is for

Reward ramp capability over a three-hour horizon.

Published checkpoints

Ramp horizon: 3 h

Who can provide it

DS3-qualified providers

Notes from the source

Three hours is the ramp horizon.

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Ramping Margin 8 RM8 upward and downward operational Response type scheduled ramping capability Trigger forecast ramp and system need Bought DS3 System Services contracts How it settles capability/performance service payment Pricing design DS3 tariff/contract rules
Full record for Ramping Margin 8 — a topic in the document is named, but not a page or table
What it is for

Reward ramp capability over an eight-hour horizon.

Published checkpoints

Ramp horizon: 8 h

Who can provide it

DS3-qualified providers

Notes from the source

Eight hours is the ramp horizon.

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Replacement reserve
Replacement Reserve De-synchronised RRD upward operational Response type manual start and dispatch Trigger TSO dispatch requirement Bought DS3 System Services contracts How it settles availability/performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Replacement Reserve De-synchronised — a topic in the document is named, but not a page or table
What it is for

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

Who can provide it

qualified de-synchronized providers

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources

The official evidence behind this row is real but incomplete, contextual or reference-only — not specific enough to state these values more firmly.

Replacement Reserve Synchronised RRS upward operational Response type manual/dispatchable synchronized reserve Trigger TSO dispatch requirement Bought DS3 System Services contracts How it settles availability/performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Replacement Reserve Synchronised — a topic in the document is named, but not a page or table
What it is for

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

Published checkpoints

Measurement window: 20 min to 1 h

Who can provide it

qualified synchronized providers

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Inertia & system strength
Synchronous Inertial Response SIR frequency support operational Response type intrinsic electro-mechanical pre-fault/post-fault inertial response Trigger instantaneous physical response to RoCoF Bought DS3 System Services contracts How it settles service payment based on declared/validated capability and performance scalars Pricing design DS3 tariff/contract rules
Full record for Synchronous Inertial Response — a topic in the document is named, but not a page or table
What it is for

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

Who can provide it

qualified synchronized units with measured inertia and reserve capability

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
Reactive power & voltage
Dynamic Reactive Response DRR reactive injection or absorption operational Response type automatic post-fault/dynamic voltage response Trigger voltage disturbance under DS3 technical tests Bought DS3 System Services contracts How it settles performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Dynamic Reactive Response — a topic in the document is named, but not a page or table
What it is for

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

Who can provide it

qualified providers meeting dynamic reactive response tests

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources

The official evidence behind this row is real but incomplete, contextual or reference-only — not specific enough to state these values more firmly.

Fast Post-Fault Active Power Recovery FPFAPR active-power restoration operational Response type automatic post-fault active-power recovery Trigger after terminal voltage has recovered to at least 85% of nominal Response checkpoint 0.25 s (90% of response) Bought DS3 System Services contracts How it settles performance-based service payment Pricing design DS3 tariff/contract rules
Full record for Fast Post-Fault Active Power Recovery — a topic in the document is named, but not a page or table
What it is for

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

Published checkpoints

Response checkpoint: 0.25 s (90% of response)

Who can provide it

qualified wind and other applicable nonsynchronous units meeting fault-recovery tests

Notes from the source

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

What the source does not state

It does not state a response deadline of its own or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which. It does publish a response checkpoint, listed with the other checkpoints in this record.

Sources
Steady State Reactive Power SSRP reactive power injection and absorption operational Response type continuous voltage/reactive-power capability Trigger voltage-control instruction and capability curve Bought DS3 System Services contracts How it settles availability/performance service payment Pricing design DS3 tariff/contract rules
Full record for Steady State Reactive Power — a topic in the document is named, but not a page or table
What it is for

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

Who can provide it

qualified providers meeting reactive capability tests

Notes from the source

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

What the source does not state

It does not state a response time or how long delivery has to be sustained, and the volume is either set per auction or not published as a standing figure — the source does not say which.

Sources
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, rendered here with wording edited for readability). 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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