A Guarantee of Origin is an electronic document issued to a producer of electricity generated from renewable energy sources.

SEMO and Guarantees of Origin

A Guarantee of Origin may be bought separately from the electricity generated. A Guarantee of Origin is valid for 12 months after the production of its unit of energy (1 megawatt-hour) and cannot be used or transferred thereafter.

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 into Irish law). The Commission for the Regulation of Utilities (CRU), after consultation with SEMO and the industry, published the Supervisory Framework for the registration, issuance, transfer and cancellation of Guarantees of Origin.

The sole purpose of GOs is for use in Fuel Mix Disclosure by suppliers.

Association of Issuing Bodies

In May 2015, SEMO, and the Irish domain, became 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). European policy makers are working on a new legal framework for the European energy market, called the Clean Energy for all Europeans package.

The SEMO Guarantees of Origin registry can be found at CMO.grexel.com. The SEMO Domain Protocol describes the Guarantees of Origin procedures in the Irish domain in more detail.

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. Applicants will be asked to agree to the terms and conditions of the Guarantees of Origin scheme (Supervisory Framework, complemented with the detail outlined in the Domain Protocol, and Business Processes) by signing the Standard Terms and Conditions.

When the application has been completed the producer/supplier will be known as an Account Holder. The first Account Holder Root User can set up additional users with specific access rights in the Guarantees of Origin registry. Account Holder Users can either be an internal member of staff, or a nominated external user. For more information on registration and users read the Guarantees of Origin Registration business process.

Current ‘Traders’ cannot register for the Guarantees of Origin scheme in Ireland.

Guarantees of Origin calendar

Guarantees of Origin are issued on a monthly basis based on validated requests received from Account Holders.


Producers in receipt of support, either REFIT (Renewable Energy Feed-in-Tariff) or AER (Alternative Energy Requirement), cannot be issued Guarantees of Origin. If a producer exits the support scheme they can apply to the Guarantees of Origin and SEMO will confirm with the Department of Communications, Climate Action and Environment (DCCAE) that they have exited the support scheme.

Contact us

A list of producers and suppliers registered in the Guarantees of Origin registry is available directly from CMO.grexel.com (Reports, Members or Plants). SEMO is the Issuing Body for Guarantees of Origin in Ireland only. For information on Guarantees of Origin for Northern Ireland please contact Ofgem.

For queries or suggestions, please contact us.