South Dublin County Council’s planning department said it had rejected the plan because of a “lack of detail of how the proposal will impact power supply once operational”.
Google’s application said around 20pc of the site’s energy needs would have been met by solar panels, but the council said this was a “significant shortfall” on the required aim of 100pc renewable energy generation.
The council added: “With regard to the power supply and electricity network, it is not clear if there is sufficient capacity within the network for the proposed development”.
Local councillors and environmental groups warned that Google’s proposed development could increase the risk of blackouts.
Seán O’Callaghan, planning officer at An Taisce, The National Trust for Ireland, warned the expansion plans would “put great pressure on an already strained electricity grid in the Dublin region”.
Gino Kenny, the socialist People-Before-Profit Teachta Dála, equivalent of an MP, for Dublin Mid-West, and two local councillors added they were “extremely concerned about the capacity of the electricity grid at this time”.
They said: “The applicant has stated that they will use the existing connection to the grid for the expansion of the data storage facility. This would have a significant impact on the capacity of the grid in the local area and could lead to blackouts in the local area.”
Data centres are energy intensive and use local water supply to cool circuitry.
Google’s proposed investment comes as tech giants seek to grow their physical infrastructure to handle demands of artificial intelligence (AI) software.