Interconnection in Ireland - The transformative impact of Greenlink on the Single Electricity Market

Market (SEM) and Great Britain (GB). This research paper analyses market arrangements, interconnector flows, market prices and indigenous renewables penetration to quantify the impact Greenlink has had on the SEM.

Greenlink improves market integration by increasing available interconnection capacity to 1,485 MW between the SEM and GB, facilitating competitive pricing through increased crossborder trading opportunities and improved flexibility. Market coupling, implicit capacity allocation and the dispatch hierarchy have enabled this additional interconnector capacity to enhance value for consumers and improve energy security and flexibility in the SEM.

Since Greenlink’s commissioning, it has become the most utilised link between the SEM and

GB compared to the Moyle and EWIC interconnectors. This has been driven by its relatively lower transmission loss factor. This efficiency makes Greenlink competitive for cross-border flows, with most energy delivered per unit transferred. Since becoming operational, the average flow on Greenlink has been a net import of c.350 MW into the SEM, causing a significant reduction in the usage of other interconnectors: 40% lower flows on EWIC and 11% less on

Moyle compared to 2023. Despite reduced utilisation of EWIC and Moyle, total interconnector flows have risen resulting in a greater portion of all-island demand now being met by net imports from GB. Figure 1 – Map of operational SEM-GB interconnectors Since January 2023, SEM prices have maintained a premium over GB. In 2024 this premium was €22/MWh. After Greenlink's launch, price convergence between GB and the SEM has improved with SEM prices averaging €17/MWh above GB; a 24% reduction in the premium.

Enhanced interconnection has allowed the SEM to import cheaper electricity when needed, lowering wholesale prices and narrowing the spread with GB.

Prior to Greenlink, Northern Ireland experienced exceptionally high levels of dispatch down of renewables due to a range of factors including falling demand, high imports from GB and constraints on the North-South tie line with the Republic of Ireland (ROI). Since Greenlink became operational, dispatch down in Northern Ireland has declined by 27% compared to 2024, despite renewables availability being the same. In contrast to this, dispatch down of renewables in ROI has increased due higher curtailments and constraints. The impact of Greenlink on renewables utilisation has therefore contrasted on either side of the border.

Greenlink’s early impact includes reducing SEM’s price premium over GB, improving price convergence, and supporting greater renewable energy integration in Northern Ireland by reducing constraints. With the Celtic interconnector due for completion in 2028 and proposed interconnection between the SEM and neighbouring countries, capacity may potentially double within the next 10 years with links to GB, France and Spain. Greenlink’s immediate impact shows that further interconnection could reduce the island’s reliance on gas-based generation and lower prices in the SEM.