Mayo Data Hub Ltd · Killala data center, Killala, Co. Mayo

Ireland's planning appeals body, An Coimisiun Pleanala, has overturned Mayo County Council's permission for Mayo Data Hub Ltd's 50-megawatt data center outside Killala in north County Mayo, ruling in September 2026 that it breached national climate policy. Mayo Data Hub, part of the US firm Avaio Digital, had won permission from the council in April 2025 despite numerous objections, including one from the author Sally Rooney. The appeal was brought by Colin Doyle of Ennis, County Clare, who had raised concerns about greenhouse gas emissions, energy use and Ireland's net zero commitments.

The 29,000 square metre facility would have included a data center, administrative buildings, electrical and mechanical plant rooms and 56 parking spaces on the outskirts of the town. Avaio Digital had put the investment at 1.5 billion euros, with 300 construction jobs and up to 35 permanent jobs, and chose north Mayo because its wind farms generate surplus power while the grid around Dublin's M50 is constrained. The company planned its own backup generators running on fossil gas and/or biodiesel.

The commission found the applicant had not shown a fixed grid connection agreement, enough capacity in existing infrastructure, significant on-site renewable power or a corporate power purchase agreement with a renewable supplier. The ruling said the applicant had not shown the project would accord with the overarching objectives of the Climate Action Plan 2025, and called it premature without evidence that it could use locally generated renewable power. Rooney had argued the data center's power demands would add to the "catastrophic planetary crisis that is global warming". Aontu TD Paul Lawless welcomed the ruling, saying Ireland was being used as "Europe's data centre", while Minister Alan Dillon said, "People want to see good jobs within reach of where they live and opportunities for young people to build their futures locally."

Data centers used 22 per cent of all electricity in Ireland in 2024, more than all urban homes combined, Lawless noted.

The ruling can be challenged only by judicial review, which must be sought within eight weeks of the decision being formally published.