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SEM meaning
Published by a LexisNexis Energy expert
What does SEM mean?
In legal and energy-sector documents, “SEM” means the Single Electricity Market for the island of Ireland, covering the Republic of Ireland and Northern Ireland, in which wholesale electricity is traded and settled under common, cross-border rules. The SEM is created by domestic legislation and regulatory instruments in both jurisdictions and implemented through the Trading and Settlement Code and related market rules. In 2018 it was reformed as “I-SEM” (to align with the EU Target Model), but “SEM” remains shorthand.
The SEM is overseen by the SEM Committee (a joint body of Ireland’s Commission for Regulation of Utilities and Northern Ireland’s Utility Regulator, with an independent member). System operation is by EirGrid and SONI; market operation is carried out by SEMO and nominated power exchanges.
Key legal features include day-ahead and intraday trading, the balancing market, imbalance settlement and the capacity remuneration mechanism. The market’s rules drive pricing, collateral, settlement and compliance obligations in generation and supply licences, PPAs, trading agreements and capacity auction documentation.
Usage is consistent across the UK and Ireland: in England and Wales and Scotland the term denotes this separate Irish market (distinct from Great Britain). The SEM continues notwithstanding Brexit under the Windsor Framework.
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View the related Practice Notes about SEM
PRACTICE NOTES
Republic of Ireland electricity market: regulatory framework, key entities, subsidies, balancing mechanisms, interconnectors and project routes to market; contrasts with Great Britain and SEM context
In the Republic of Ireland, electricity is governed by network, regulatory, policy and retail frameworks that differ from those in Northern Ireland. Although the two jurisdictions share a wholesale platform—the Single Electricity Market (SEM)—all other market arrangements remain separate. For further detail on the SEM, see Practice Note: Island of Ireland Single Electricity Market (SEM)—an introduction. Key entities within the RoI electricity market The RoI electricity sector can be described as consisting of: participants active in the all-island SEM with operations based in Ireland renewable and thermal generators, and suppliers within Ireland, specifically licensed by the Commission for Regulation of Utilities (CRU) under section 14 of the Electricity Regulation Act 1999 the distribution network and related metering equipment, owned and run by ESB Networks the transmission system, owned by ESB Networks and operated by EirGrid interconnectors linked to RoI networks, including the Louth–Tandragee North–South Interconnector (NS Interconnector) and the East–West Interconnector (EWIC) end users connected to these networks, supplied by...
21 May
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PRACTICE NOTES
All-Island Single Electricity Market (Republic of Ireland and Northern Ireland): post-Brexit legal and regulatory overview, market structure, codes, participants, interconnectors and trading (DAM/IDM/Balancing, capacity, FTRs, CfDs)
Brexit impact At 11 pm (GMT) on 31 December 2020, the transition/implementation period that followed the UK’s exit from the EU drew to a close. This moment—known in UK law as ‘IP completion day’—brought key transitional measures to an end and triggered major shifts across the UK’s legal framework. Any alterations pertinent to this content will be detailed below. From IP completion day, the European Union (Withdrawal) Act 2018 (EU(W)A 2018) established a fresh class of domestic UK law—retained EU Law (REUL)—comprising EU-derived rights and instruments that were kept in force in the UK after Brexit. On 29 June 2023, the Retained EU Law (Revocation and Reform) Act 2023 (REUL(RR)A 2023) received Royal Assent. REUL(RR)A 2023 reshapes how REUL is handled by: revoking large tranches of REUL from 31 December 2023 re-labelling REUL as ‘assimilated law’ from 1 January 2024 creating new powers concerning assimilated law This reclassification of REUL (and related expressions) as assimilated law signifies a shift...
21 May
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PRACTICE NOTES
Northern Ireland electricity market: legal framework, SEM post-Brexit (NI Protocol), key entities, interconnection, and renewables support (NIROCs, closures, fixed-price proposals, future auctions, climate targets)
Brexit and the Single Electricity Market The withdrawal agreement between the UK and the EU, in force from 1 February 2020, expressly makes provision for the island of Ireland’s Single Electricity Market (SEM) within the NI Protocol (the Protocol), ensuring NI remains subject to defined EU rules so the SEM can keep operating. Accordingly, there have been no major alterations to the SEM since IP completion day, for the time being. That position could, however, potentially shift if the two legal regimes begin to diverge over time in the two jurisdictions. Under the Protocol, specific EU measures concerning electricity generation, distribution, transmission, supply and trading continue to apply in NI for a minimum of four years after the end of the transition period. After this first four‑year term (ending in December 2024), and after each following four‑year term, NI may choose to leave the Protocol on the basis of ‘democratic consent’, most likely through an NI referendum. The Protocol would then stop applying after a further two‑year interval while...
21 May
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