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Generator: Frequently Asked Questions 

Prerequisites to Joining the Market

Before an application to register units in the Single Electricity Market can be considered, there are pre-requisite criteria that must be fulfilled.


Contact with the following organisations will be required in order to meet the pre-requisites of registration.


Northern Ireland

Republic of Ireland

Regulatory Authorities



Metered Data Provider

Distribution Connected



Transmission Connected



Connection Agreements

Distribution Connected - DSO


ESB Networks

Transmission Connected - TSO



Use of System Charges

Distribution Connected - DUOS


ESB Networks

Transmission Connected - TUOS



Generator Unit Types in SEM

There are several distinct types of Generator Units for the purposes of participation in the Single Electricity Market. To help you determine which is the correct category for your unit registration, please answer the questions below :

1. Is the Generator Unit dispatchable by the relevant System Operator?
  • If the Generator Unit is dispatchable, then proceed to Decision 2
  • If the Generator Unit is not dispatchable it is classed as Autonomous, then
  • proceed directly to Decision 3

2. Is the availability of the Generator Unit’s fuel source variable (limited to wind or run-of-river hydro) in the short-term?
  • If the Generator Unit’s fuel source is variable in the short term, and the fuel in question is wind or run-of-river hydro, it is classed as a Variable Generator Unit
  • If the Generator Unit’s fuel source is not variable in the short term, and/or the fuel in question is not wind or run-of-river hydro, it is classed as a Predictable Generator Unit
  • in both cases, then proceed to Decision 3

3. Is the Generator Unit to be included in the price setting process?
  • If the Generator Unit is Autonomous, it must be registered as a Price Taker
  • If the Generator Unit does not have Priority Dispatch status, it must register as Price Maker
  • If the Generator Unit does have Priority Dispatch status, it can choose to register as a Price Maker or as a Price Taker (and can change status between the two with 29 days notice)

Special Units

Special provisions exist for certain types of Generator Unit. The table below outlines these units, alongside a summary of their role in the market and their settlement class.



Settlement Class

Demand Site Unit

Demand site which offers an ability to deliver demand reduction in response to dispatch instructions

Predictable Price Maker Generator Unit

Energy Limited Generator Unit

Hydro-electric generator which has a physical energy limit

Predictable Price Maker Generator Unit

Interconnector Unit

Unit which allows Interconnector users to trade between SEM and BETTA

Predictable Price Maker Generator Unit

Interconnector Error Unit

Unit to which imbalance on an Interconnector is allocated for settlement

Autonomous Generator Unit

Interconnector Residual Capacity Unit

Unit which allows SO to utilise/trade spare interconnector capacity

Predictable Generator Unit, but neither a Price Maker of a Price Taker

Pumped Storage Unit

Generator Unit within a pumped storage plant

Predictable Price Maker Generator Unit

Trading Sites

All Generator Units must be registered as part of a Trading Site. A Trading Site refers to one or more Generator Units and either a Trading Site Supplier Unit (covered by a single connection agreement or located collectively on a contiguous site) or an Associated Supplier Unit.

Netting Generator Units

A Netting Generator Unit must be registered by the Market Operator as part of eachTrading Site (see Section 2.5 for more details regarding Trading Sites). A NettingGenerator Unit is a notional Generator Unit registered to facilitate settlement of a Trading Site. Netting Generator Units do not physically exist, have no meter associated with them and are treated as Autonomous Generator Units for most purposes.

How do I register a Generator Unit?

The following details the documentation and fee that is required by SEMO

Documents Required

Northern Ireland Applications

Republic of Ireland Applications

Participation Notice



Participation Fee

£2,701.98 (incl.VAT)
£2,251.65 (excl. VAT)

€3,210.30 (incl. VAT)
€2,610 (excl. VAT)

Finance Data Spreadsheet



Collateral Data Spreadsheet



Generator Unit Spreadsheet



Form of Authority and Proof of Consent

If applying as an intermediary

If applying as an intermediary

  • Participation Notice
    The Participation Notice is the application form which an applicant must complete if they wish to register a unit or units in the Single Electricity Market. The data the applicant provides will be used by the Market Operator in order to progress the participants application.
  • Participation Fee
    The Participation Fee is charged per unit and the currency in which it is paid is decided on by the location of the actual unit. Companies who are VAT registered outside ROI & UK (including NI) pay rates excl.VAT. If you have any questions before paying your Participation Fee, please contact to confirm the appropriate fee.
  • Financial Data
    The financial data document captures the bank details of the applicant.
  • Collateral Data
    An applicant must provide expected generation volumes for five months. This allows the applicants credit cover requirement to be calculated.
  • Generator Unit Spreadsheet
    This spread sheet provides technical and general information to the Market Operator such as contact details, default bids etc.
  • Form of Authority and Proof of Consent
    Form of Authority and Proof of Consent will be required if the application is by an intermediary.

Please post the completed Participation Notice and Participation Fee (Form of Authority and Proof of Consent also if applicable) to:

  • SEMO Customer Service
  • The Oval
  • 160 Shelbourne Road
  • Ballsbridge
  • Dublin 4

Please email the completed spreadsheets which accompany the Participation Notice to:

What happens next?...

Once SEMO have received the participation fee and the application pack has been validated as complete you will be issued with a receipt for your application. This starts the registration process. The various documents submitted will be circulated to all relevant parties such as the System Operator, Meter Data Provider and within SEMO :

  • The TSO will validate Technical Offer Data
  • The Meter Data Provider will ensure the meter feeds to SEMO are correctly configured
  • SEMO Credit Risk Management will calculate collateral credit cover requirements
  • SEMO Funds Transfer will validate bank details for new Participants
  • SEMO IT will provide details for Communication Channel Qualification Testing

Once these tasks, and any clarifications required, have been addressed and completed all parties will be in a position to discuss an effective date for the unit to enter the market. This proposed effective date may require certain issues to be addressed at least five working days before the effective date. Providing all requirements have been met the unit will enter the market and a Commencement Notice will be issued to the Participant.

SEMO Registration will also be facilitating Participant Readiness during this process to ensure a smooth transition to becoming a Participant.  This session is intended to introduce you to the market systems and the core operational functions you would be interfacing, as a Participant in the SEM.

If you need any further information on joining the market or require assistance with your application please email :

SEMO is a joint venture between EirGrid PLC and SONI Limited