SEMO and Guarantees of Origin

A Guarantee of Origin is an electronic document that proves to a final customer that a quantity of electricity originated from a specific renewable energy source. The Guarantee of Origin tracks renewable energy production to the final customer, providing full transparency for these consumers.

Each Guarantee of Origin

  • Represents 1 megawatt-hour of electricity produced; and
  • Contains all relevant registration information related to the production device

SEMO operates the registry for Guarantees of Origin in Ireland available at G-REX (



SEMO was nominated as the Issuing Body for Guarantees of Origin in Ireland in Statutory Instrument No. 147 of 2011 and No. 483 of 2014 (which transposed EU Directive 2009/28/EC regarding the promotion of the use of energy generated from renewable sources into Irish law). The Supervisory Framework published by the Commission for the Regulation of Utilities (CRU), after consultation with SEMO and the industry, outlines the GO processes applicable in Ireland.

The EU has agreed a comprehensive update of its energy policy framework called the "Clean Energy Package for all Europeans package". Following "political agreement by the Council and the European Parliament in 2018 and early 2019, enabling all of the new rules to be in force by mid-2019, EU countries have 1-2 years to transpose the new directives into national law".


Association of Issuing Bodies

SEMO is a member of the Association of Issuing Bodies (AIB). AIB facilitates the international exchange of Guarantees of Origin via the inter-registry telecommunications hub (AIB hub). To support international trade of Guarantees of Origin, AIB developed a standardised system called the European Energy Certificate System (EECS). The SEMO Domain Protocol outlines how Guarantees of Origin procedures in Ireland align with the EECS rules.


GO scheme

Any electricity producer (not in receipt of support) or supplier active in the Irish domain can register as an Account Holder in the GO scheme by contacting

Applicants will be asked to agree to the Standard Terms and Conditions for the scheme. When the application has been completed, the producer/supplier becomes known as an Account Holder and the Account Holder Root User is sent their credentials for login to The Root User can then process GO transactions for the Account Holder including:

  • Production Device Registration, and requesting the issue of Guarantees of Origin
  • Transferring GOs to other Account Holders in Ireland, or importing/exporting GOs from and to other European Member States
  • Cancellation of Guarantees of Origin for use in Fuel Mix Disclosure (by suppliers only)

For more information on these procedures, refer to the SEMO business processes or request a call back from the Guarantees of Origin team.

Currently ‘Trader only’ accounts are not permitted in the Guarantees of Origin scheme in Ireland.

Guarantees of Origin Timelines

SEMO in its capacity as the issuing body of Guarantees of Origin are required to issue Guarantees of Origin in accordance with an agreed upon timeline. The timeline for the coming year can be found below

Production MonthMeter data available in Online RegistryAccount Holder Submit GO Request BySEMO Issues GO's By 
  Issue Month + 11 WD Issue Month + 15 WD Last WD of the month ROI Bank Holidays
Dec 18/01/2022 24/01/2022 31/01/2022 New Years Day Observed (Mon 3 Jan 2022)
Jan 15/02/2022 21/02/2022 28/02/2022  
Feb 15/03/2022 22/03/2022 31/03/2022 St Patricks Day (Wed 17 Mar 2022)
Mar 15/04/2022 22/04/2022 29/04/2022 Easter Monday (Mon 18 April 2022)
Apr 17/05/2022 23/05/2022 31/05/2022 Early May Bank Holiday (Mon 2 May 2022)
May 16/06/2022 22/06/2022 30/06/2022 June Bank Holiday (Mon 6 Jun 2022)
June 15/07/2022 21/07/2022 29/07/2022 -
July 16/08/2022 22/08/2022 31/08/2022 August Bank Holiday (Mon 1 Aug 2022)
Aug 15/09/2022 21/09/2022 30/09/2022 -
Sep 17/10/2022 21/10/2022 28/10/2022 October Bank Holiday (Mon 31 Oct 2022)
Oct 15/11/2022 21/11/2022 30/11/2022 -
Nov 15/12/2022 21/12/2022 30/12/2022 -
Dec 17/01/2023 23/01/2023 31/01/2023 New Year's Day (Fri 1 Jan 2023)