Information regarding cookies and WWW.SEM-O.COM

By using this website, you consent to the use of cookies in accordance with the Single Electricity Market Operator’s Cookie Policy.
For more information on cookies and our Cookie Policy please follow this link.

I accept

 About SEMO 

The Single Electricity Market

SEM At a Glance

The Single Electricity Market (SEM) is the wholesale electricity market operating in the Republic of Ireland and Northern Ireland. As a gross mandatory pool market operating with dual currencies and in multiple jurisdictions the SEM represents the first market of its kind in the world.

The Single Electricity Market provides for a competitive, sustainable and reliable wholesale market in electricity aimed to deliver long-term economic and social benefits that are mutually advantageous to Northern Ireland and the Republic of Ireland.

The market encompasses approximately 2.5 million electricity consumers, 1.8 million in the Republic of Ireland and 0.7 million in Northern Ireland.

The Single Electricity Market Operator

SEMO Vision & Values

The Single Electricity Market Operator (SEMO) facilitates the continuous operation and administration of the Single Electricity Market. SEMO is a joint venture between EirGrid plc and SONI Limited. The organization is managed as a contractual joint venture between EirGrid, the transmission system operator for the Republic of Ireland, and the System Operator for Northern Ireland (SONI). SEMO is licensed and regulated cooperatively by the Commission for Energy Regulation (CER) in Ireland and the Northern Ireland Authority for Utility Regulation (NIAUR).


In August 2004 a memorandum of understanding was signed by the CER and NIAUR.The memorandum of understanding established a series of principles for the development of a single wholesale electricity market for the Republic of Ireland and Northern Ireland.In November 2004 a development framework for the All Island Market for Electricity was agreed upon by the Irish Department of Communications, Marine and Natural Resources (DCMNR), the Northern Ireland Department of Enterprise, Trade and Development (DETI), the CER and the NIAUR.

An additional memorandum of understanding was agreed upon in June 2005 between the respective transmission system operators in the Republic of Ireland and Northern Ireland. ESB National Grid (ESBNG), now EirGrid, and SONI committed to combining their resources to work cooperatively towards the establishment of a single electricity market.The agreement between EirGrid and SONI to establish the market was formally acknowledged and approved by the CER and NIAUR on the 10th of June 2005.

SEM Establishment Programme

The SEM Establishment Programme commenced in 2005 with a clear focus to bring about the single electricity market. Managed by both EirGrid and SONI the SEM Establishment Programme was responsible for the establishment of SEMO and the systems and processes necessary to operate the new market.

The programme encompassed three broad project areas: Single Electricity Market Implementation, Single Electricity Market Operator Establishment and Transmission System Operator Readiness.

SEMO is a joint venture between EirGrid PLC and SONI Limited