SONI Publishes Final Results of T-4 2023/2024 Capacity Auction for the Single Electricity Market

SONI, (the Electricity System Operator for Northern Ireland) has published the final results of the latest capacity auction for the Single Electricity Market which took place on the 27th of April. There are no changes to the provisional results (hyperlink to statement) which were published on May 5th.  

The final results have been approved by the Single Electricity Market Committee (SEMC) which is made up of representatives from regulators in Northern Ireland (the Utility Regulator) and Ireland (the Commission for the Regulation of Utilities) and two independent members.

The capacity auction is a key element of the all-island wholesale electricity market and is designed to deliver a reliable electricity supply at the least possible cost.  The auction also aims to encourage new and efficient power plants into market; but only if these are competitive and economical solutions. The auction procured sufficient capacity to meet security of supply for the period October 2023 to the end of September 2024.

The T-4 auction has secured a total of 7,322 megawatts (MW) of capacity for the island, with 1,924 MW of this capacity for Northern Ireland.

Of the 124 generating units that took part in the auction, 115 were successful, 35 of these in Northern Ireland. A total of £343 million of capacity payments will be paid to generators who were successful, £107 million of which will be paid to Northern Ireland generators. The auction clearing price was 43,666 £/MW per year.

The final results are available at

SONI has also published the following documents on the SEMO website:

Note to editors:

The T-4 capacity auction is part of a series of changes made to the Single Electricity Market to increase cost efficiency and competitiveness. The improvements to the market have integrated the all-island electricity market with European electricity markets. The new arrangements maximise efficiency of electricity trading on interconnectors. It is also designed to encourage new investment and innovation.

The market was designed by the SEMC. This design was implemented by SONI in Belfast and EirGrid in Dublin and the upgraded market has been live since October 1st 2018.

T-4 auctions take place every year, with the next scheduled for January 2021.

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