New data centre connection rules EirGrid and ESB Networks publish data centre connection processes

What you need to know

• Data centres under 20 MVA apply to ESB Networks, while those requiring 20 MVA or more apply to EirGrid
• The onsite generation requirements align with the CRU’s LEU decision – it must be sufficient to meet 100% of the site's MIC
• Data centres must meet at least 80% of their annual electricity demand through new Irish renewable generation
• Detailed locational network constraint parameters have now been published by EirGrid and ESB Networks – Dublin is currently entirely constrained
• Clarity has been provided on the exact planning status requirements for data centres, onsite generation and renewable generation

Grid application processes

Both EirGrid and ESB Networks, in their respective capacities as Transmission System Operator (TSO) and Distribution System Operator (DSO), published their engagement and connection processes for data centre applicants, implementing the CRU's Large Energy Users Connection Policy[1] (the LEU Policy) published in December 2025. EirGrid and ESB Networks have detailed the connection processes, and the assessment criteria against which applications will be measured. These include outlining locational constraint information to identify areas of the network where new connections may or may not be accommodated.

The LEU Policy sets out different generation requirements depending on the size of the data centre:

1. Below 1 MVA (de minimis): No substantive generation requirements apply. However, ESB Networks will still carry out a locational assessment to determine whether the connection can be accommodated in a constrained area.
2. 1 MVA to less than 10 MVA: The data centre must provide an autoproducer unit (i.e. a unit that can both import and export, participating in the Single Electricity Market) with de-rated capacity sufficient to meet 100% of the site's Maximum Import Capacity (MIC).
3. 10 MVA and above: The data centre must provide dispatchable onsite or proximate generation and/or storage capacity, separately connected and metered, with de-rated capacity sufficient to meet 100% of the site's MIC and mandatory participation in the wholesale electricity market.

In all cases at or above the de minimis level, the data centre must also demonstrate a credible plan to meet at least 80% of its annual electricity demand through new Irish renewable generation, within a six-year glide path from energisation.

We will be publishing a more detailed analysis in due course, however, initial noteworthy issues coming out of published connection processes are:

• Capacity threshold: Data centres with an expected MIC in excess of 20 MVA must apply to be connected to the transmission system with EirGrid.
• Effective from: Applies to data centres seeking connection from 12 December 2025.
• Planning: Both processes place emphasis on the planning status of the data centre, nominated generation and renewable generation, as applicable, at each stage of the application. Developers should note the following requirements from the outset:
  • For EirGrid, a validated planning application for the data centre must be in place before the mandatory pre-application meeting, which must take place before any formal application can be submitted.
  • For ESB Networks, a valid planning application for the data centre site must be in place by the batch closing deadline. For autoproducer applicants (MIC between 1 MVA and less than 10 MVA), the PAN requirements are slightly different. For those applicants, evidence of a valid planning application is required for both the dispatchable generation and the data centre site at PAN stage, rather than just the generation. In addition, there is no requirement to clarify third-party generation arrangements or ECP-GSS status at that stage.
  • Both ESB Networks and EirGrid require full planning permission for the “Nominated Generation”. The “Nominated Generation” refers to the new dispatchable onsite or proximate generation or storage capacity required to match the data centre's MIC and participate in the wholesale electricity market. This planning permission must also be free of any judicial review period when applying. It should be noted that for ESB autoproducer applicants full planning permission for the “Nominated Generation” is required by the batch closing deadline rather than at ECP-GSS entry.
  • Both ESB Networks and EirGrid require evidence of a submitted planning application for the “Nominated Renewables” at application stage, with full permission required prior to offer acceptance. The “Nominated Renewables” are the additional Irish renewable generation required to meet the 80% annual electricity obligation.
• Fault ride-through: EirGrid have noted that “[t]he progression of any new capacity is based on the assumptions that the existing data centre fault ride-through issues are resolved, that any new data centre connections do not contribute to fault ride-through issues and that they do not introduce any new issues in relation to the behaviour of their demand profile.”
• Queue: The policy adopts a “first come, first served” approach for interacting applications, while recognising that later applications may impact connection methods, costs and timelines.
• Ongoing judicial review: EirGrid notes that the policy remains subject to ongoing judicial review proceedings relating to the LEU Policy and may change depending on the outcome of those proceedings.
• “New” renewable generation - There appears to be a conflict in the EirGrid policy document which merits clarification. The EirGrid policy document notes that for nominated renewables to have a credible prospect of being delivered that these must either have “an existing connection agreement, live offer, application in train, or submit an application into the ECP-GSS process”. However, at a later point the EirGrid policy document indicates that “the associated generation project(s) must have applied to the ECP‑GSS connection process”. It seems unusual that renewables projects that have applied for, or already secured, their grid connection offer or agreement but not yet secured a route-to-market could not be considered “new” solely because they did not obtain their connection through ECP-GSS.

Constrained Area - EirGrid

As part of any data centre connection application, EirGrid or ESB Networks as appropriate, will carry out a locational assessment to determine if the proposed data centre is located in a constrained area of the network. EirGrid has published a Constrained Area Overview alongside Data Centre Connection Offer Process and Policy V3. Some initial points for developers to consider are:

• The Greater Dublin region is considered fully constrained for large data centre development.
• EirGrid's high-level assessment indicates that some capacity may be available on the 220 kV network in the Galway, Limerick and Cork areas. This is estimated to be in the order of 50–100 MW per location or 150–300 MW in total, with figures potentially larger where renewable generation connects at the same transmission node as the data centre.
• However, many existing 220 kV nodes capable of accommodating new capacity have significant refurbishment programmes already scheduled, and new connections at those locations are unlikely before the mid-2030s.
• As part of any connection application, EirGrid will carry out a network locational assessment. EirGrid has submitted a proposed approach for locational heat maps to the CRU for approval. The maps will identify where potential demand capacity could be located across the transmission system. In the interim, locational information is available in EirGrid's Data Centre Constrained Area Overview, which was recently published May 2026. Full heat maps are expected to be made available via the 2027 Ten Year Transmission Forecast Statement.

Constrained Area - ESB Networks

As part of every data centre connection application, ESB Networks carries out a locational assessment to determine whether the proposed data centre is in a constrained area of the distribution network. ESB Networks has provided more details on its own constrained area assessment methodology, and some initial points for developers to consider include:

• The assessment is carried out across 27 distribution planning zones as defined in the Distribution Network Development Plan, with each application assessed on a case-by-case basis.
• The following criteria are used to assess whether a demand application is in a constrained distribution planning zone:
  1. Whether there is firm capacity available at the voltage level where connection is requested
  2. Whether there is firm capacity available at any voltage level upstream, including the connection point to the transmission system, and
  3. Whether an application reduces the available firm capacity at the voltage level where connection is requested, or any voltage level upstream, to less than 20% of the available firm capacity for demand connections.
• The assessment follows a two-step process:
  1. Whether the relevant distribution planning zone is constrained in aggregate, based on available firm capacity at all high-voltage substations in the zone, and
  2. Where the planning zone is not constrained, whether the specific substation where connection is requested is constrained. Where a specific substation is constrained, ESB Networks will assess whether load transfers between substations in the same planning zone can be undertaken to bring the connecting substation into compliance.
• ESB Networks will publish and annually update information on its website identifying which distribution planning zones are constrained.

Comment

These connection processes reshape how data centres secure power in Ireland. Meeting these rules requires early planning and strict policy compliance. Developers must act now to evaluate regional grid capacity and planning timelines.

For expert compliance guidance, contact our Energy team.

The content of this article is provided for information purposes only and does not constitute legal or other advice.

[1] CRU/2025236