<article><p class="lead">The Irish all-island integrated single electricity market (I-SEM) will continue even if the UK leaves the EU without a withdrawal agreement, but cross-border trade with Great Britain would become much less efficient, the Irish and Northern Irish energy regulators have said. </p><p>All-island trade within I-SEM would continue as is, the regulators said. But trade between I-SEM and Great Britain "will almost certainly be less efficient than today as Great Britain will no longer be part of the pan-EU market and the SEM will become an isolated market."</p><p>The day-ahead market would likely be local only in the event of a hard Brexit, Irish transmission system operator (TSO) Eirgrid said. The TSO will work on a new cross-border arrangement, "but we assume this will not be implemented on day 1", it said in a presentation to stakeholders. </p><p>The intra-day market and balancing market would continue as is, with cross-border trade continuing unaffected. This could lead to some liquidity being drawn to the intra-day auctions, Eirgrid said.</p><p>The Irish T-4 capacity market auction for 2022-23 will go ahead as planned on 28 March. Contracts awarded will be honoured regardless of any type of Brexit, the regulators said. </p><p>The UK government last year said that <a href="https://direct.argusmedia.com/newsandanalysis/article/1772113">contingency plans</a> were being drawn up for a separate Northern Ireland power market, but the <a href="https://direct.argusmedia.com/newsandanalysis/article/1778344">UK energy minister</a> and <a href="https://direct.argusmedia.com/newsandanalysis/article/1797188">Eirgrid</a> both expressed confidence it could continue post Brexit. </p></article>