An Coimisiún Pleanála has overturned planning permission for a proposed data centre in Killala, County Mayo, following third-party appeals against the development.

The proposal, submitted by Mayo Data Hub Ltd, sought to construct a high-capacity data facility spanning more than 29,000 square metres at Killala Business Park. Mayo County Council had granted conditional approval for the project, which was positioned to utilize local infrastructure in the west of Ireland.

However, the local decision was appealed to the national planning authority by several objectors, including international bestselling author and County Mayo resident Sally Rooney. In her submission to planning authorities, Rooney had urged refusal of the project, citing concerns regarding environmental impact, carbon emissions, and the high proportion of national electricity consumed by data infrastructure.

In overturning the approval, An Coimisiún Pleanála ruled that the developers failed to demonstrate sufficient available local electricity capacity or secure a compliant on-site renewable energy supply in line with national climate policy. The board concluded that the proposed development did not satisfy mandatory requirements governing large energy users and national grid sustainability obligations.

Planning consultants acting on behalf of the applicant had previously contended that the facility would attract tech-sector investment to the region, arguing that the electricity grid in the west of Ireland had adequate capacity outside constrained urban areas.

The refusal underscores increasing regulatory scrutiny surrounding energy consumption by data centres as Ireland seeks to align industrial development with binding carbon reduction targets.