Ireland's data centre grid rules: what CRU/2025236 changed

Since 12 December 2025, new data centres in Ireland must bring dispatchable generation or storage matching their maximum import capacity, and source at least 80 percent of their annual power from new Irish renewables. EirGrid says the greater Dublin area is fully constrained, so growth is steered west and to planned sites.

Ireland is the clearest case in Europe of a country where data centres grew faster than the grid could comfortably carry. This post explains the rules in plain language, using the grid operator's own May 2026 documents, the national statistics office and law firm summaries of the regulator's papers. It separates what is written down from what is still being tested in court, and it labels every figure with its source and date.

Key numbers at a glance

• Data centre share of Ireland's metered electricity: 23 percent in 2025, up from 5 percent in 2015 (Central Statistics Office, release on 2025 data).
• Data centre consumption: 7,663 GWh in 2025, up 10 percent from 6,973 GWh in 2024, same release.
• Contracted data centre demand: 2 GW, mostly in greater Dublin, which EirGrid says would be nearly a third of all demand in Ireland once fully used (EirGrid Constrained Area Overview, 20 May 2026).
• Further interest: about 6 GW more, which EirGrid says would double the current system peak, from a market intelligence exercise it ran at the regulator's request (same document).
• System size: All-Ireland peak demand of about 7.5 GW, on a synchronous island with limited links to other grids (same document).
• Policy date: the regulator's decision CRU/2025236 was published on 12 December 2025.
• Projected share: 31 percent of Irish electricity demand by 2034 based on existing contracts, a regulator projection reported by Philip Lee on 22 December 2025.
• Where growth may fit: 50 to 100 MW per site on the 220 kV network around Galway, Limerick and Cork, 150 to 300 MW in total, as a high level desktop assessment by EirGrid (same document).
• Business electricity price: 0.2552 euro per kWh in the second half of 2025, the highest in the EU, against an EU average of 0.1837 (Eurostat, medium sized non-household consumers, excluding VAT).

How big data centres became

EirGrid describes data centres as one of the most significant drivers of overall growth in Irish electricity demand. The Central Statistics Office measures metered consumption, and its release on 2025 data shows data centres used 7,663 GWh, or 23 percent of the total. In 2015 they used 1,240 GWh, which was 5 percent. Other metered customers grew by only 2 percent in 2025, while data centres grew by 10 percent. Quarterly use rose from 291 GWh at the start of 2015 to 1,991 GWh in the last quarter of 2025, an increase of 584 percent. The same release shows large energy users, a category that includes big data centres, at 33 percent of total consumption.

The CSO page for this release shows two dates, 7 July 2025 in the header and 7 July 2026 in the statistician's comment. Data for 2025 can only have been published in 2026, so the July 2026 date is the consistent one.

How did a small country take on so much? EirGrid explains it in its May 2026 overview. In the 1970s and 1980s, multiple 220 kV and 400 kV circuits were built to bring power into Dublin, including two 400 kV circuits from Moneypoint. That gave the Dublin region far more capacity than other areas. When data centres arrived, the capacity was already there, and EirGrid says Ireland was able to contract over 2 GW of data centre demand without significant network reinforcements. That headroom, in its words, has now largely been exhausted.

Why the grid says Dublin is full

EirGrid names five challenges in its overview. They are worth understanding because they explain why the rules look the way they do.

Network capacity. Moving very large point loads through existing lines, cables and transformers is getting harder. EirGrid says planned works for the 2026 to 2030 price control period cover many needs, such as offshore wind connections and refurbishment, and need to be supplemented to carry more data centres.

Short circuit levels. When a fault happens, very high currents flow. If they exceed what circuit breakers can interrupt, equipment and people are at risk. Dublin has high short circuit levels already. Adding conventional generators near new data centres, which the rules require, would raise them further. Until more 400 kV network is built, EirGrid says generator connections on the 220 kV and 110 kV network cannot be accommodated in greater Dublin. That is the main reason it calls the region fully constrained.

System stability. EirGrid reports recent fault ride-through problems, where data centres rapidly cut their demand in response to voltage dips. A sudden large drop in demand creates a mismatch between supply and demand and shifts the frequency of the whole system. It also warns that the oscillating demand pattern of AI data centres could be a stability risk. Ireland is a synchronous island with limited direct current links, so it has less outside help than a country wired into a continental grid. EirGrid points out that Ireland's peak demand is smaller than that of greater London.

Security of supply. The system needs enough dispatchable generation to meet demand at every moment. EirGrid says Ireland has had recent difficulties delivering new capacity awarded through the capacity market.

Outages. Building the planned reinforcements requires taking lines and substations out of service, and each new connection adds to an already crowded outage plan.

How the policy got here

The December 2025 decision is the end of a process that ran for four years. Mason Hayes and Curran, an Irish law firm, set out the earlier steps in a February 2025 note.

• November 2021: the regulator issued direction CRU/21/124 to EirGrid and ESB Networks, setting criteria for assessing data centre connection applications. The firm describes it as a reactive, short term measure.
• Early 2024: consultation CRU2024001 opened a longer term look at how large energy users should connect to the electricity and gas systems. It introduced mandatory demand curtailment, a power for the system operators to direct a user to cut or stop its imports at short notice.
• 18 February 2025: the regulator published a proposed decision, CRU202504. It required dispatchable generation or storage on or near the site, taking part in the wholesale market, but set no minimum renewable purchase. Data centres would only have to report their renewable use and emissions each year. Consultation closed on 4 April 2025.
• 12 December 2025: the final decision, CRU/2025236, kept the dispatchable requirement and added the 80 percent renewable rule described below.

The renewable rule is the clearest change between draft and final. Philip Lee, another Irish firm, wrote on 22 December 2025 that the regulator grounded it in its renewable policy function under section 9(1)(s) of the Electricity Regulation Act 1999, not in an emissions cap. The same note reports the regulator's context figures: data centres at around 22 percent of national electricity use, roughly half of metered use in the Dublin and Meath region, and a projected 31 percent of Irish demand by 2034 based on existing contracts. That projection is the regulator's, as relayed by the firm, not a measured outcome.

What the new rules require

The regulator, the Commission for Regulation of Utilities, published its Large Energy Users Connection Policy decision, CRU/2025236, on 12 December 2025. It replaces the earlier direction CRU/21/124. Applications received before the decision continue under the old direction. The new policy applies only to data centres. The summary below comes from EirGrid's Data Centre Connection Offer Process and Policy Version 3, dated 20 May 2026, which EirGrid says it issued under a direction from the regulator in decision CRU/2025236, and from law firm summaries of the decision paper.

Size matters. Rules depend on a site's maximum import capacity, the most power it may draw from the grid.

• Below 1 MVA: a de minimis threshold. Most of the policy does not apply, though EirGrid must still consider location when assessing requests.
• 1 MVA up to 10 MVA: the site must provide an autoproducer unit that covers its maximum import capacity on a de-rated basis, and that unit must take part in the wholesale electricity market.
• 10 MVA and above: the site must provide dispatchable onsite or nearby generation or storage covering its maximum import capacity, again on a de-rated basis. The generation must be separately connected and metered and must take part in the market. The data centre cannot operate or ramp up until that generation is delivered.

Who handles an application depends on size. EirGrid's demand connections page says facilities under 20 MVA at a single location apply to ESB Networks, the distribution operator, and connections of 20 MVA or above apply to EirGrid.

Three further conditions matter. First, the backup must be new. It cannot already hold a capacity market contract and must not rely on existing system capacity. Second, it cannot be subject to run-hour limits that would stop it operating on an ongoing basis, other than routine maintenance. Third, project splitting, meaning dividing a large project to qualify as smaller ones, is not permitted.

On renewables, sites above the threshold must show they can meet at least 80 percent of annual demand from additional renewable electricity generated in Ireland. Each must submit a glidepath plan, and the nominated renewable projects must already have applied to the generation connection process. A&L Goodbody and Philip Lee both report that developers have six years from energisation to comply. The contribution of that renewable generation, up to 80 percent of annual demand, counts against the dispatchable generation requirement on a de-rated basis, so the two obligations overlap rather than simply add up.

Compliance brings one benefit. Philip Lee reports that sites meeting the generation requirement are exempt from mandatory demand curtailment, the short notice cut described above, which the Mason Hayes and Curran note says is widely regarded as incompatible with how data centres prefer to run. Enforcement runs the other way too: if the nominated generation or storage misses its performance and availability standards, the import capacity can be reduced or moved to a non firm basis, meaning it can be interrupted.

The policy also allows refusal on location. EirGrid and ESB Networks assess applications case by case, and applications may be refused in constrained areas, including those below the de minimis threshold.

How the application works, step by step

EirGrid's process document lays out nine stages. The key ones are below.

1. An optional early meeting to test whether a project could connect.
2. A mandatory pre-application meeting, which requires a validated planning application for the data centre.
3. Formal submission, with dynamic models for stability analysis, the renewable glidepath, details of the nominated generation, confidentiality agreements and a 7,000 euro first payment.
4. A completeness review, after which EirGrid may request more information, ask for the balance of fees, or terminate the application if criteria are clearly not met.
5. Offer preparation and issue. The offer is valid for two calendar months and lapses if not accepted.
6. Acceptance, which requires that the nominated generation has accepted its own connection offer.
7. Obligations for the life of the project. The generation must stay operational, and if it fails or withdraws the data centre needs a credible plan for immediate replacement or faces a cut in import capacity or disconnection.

Applications are made by email for now. EirGrid's demand connections page says an online application portal is still being developed.

Timing depends on the generation. If the nominated generation already has connection offers, the standard processing time is about seven and a half months from a complete application and fee to an offer. If the generation has only just applied, it can be up to eighteen months, because the data centre cannot be progressed ahead of the generation it relies on.

Where growth can still happen

EirGrid's overview is frank. It says greater Dublin and the surrounding areas are expected to be constrained for large data centres. It adds that demands above 50 MW of continuous load are extremely large for the 110 kV network, so projects that size need to connect at higher voltages.

For other regions, a 2023 roadmap identified room for about 300 MW of extra data centre demand outside Dublin, on assumptions that Dublin demand did not grow beyond 1.3 GW and that 80 percent of consumption was matched by renewables. A new high level assessment finds 50 to 100 MW per site on the 220 kV network around Galway, Limerick and Cork, so 150 to 300 MW in total, possibly more if renewables connect at the same point as the data centre. EirGrid also warns that many 220 kV substations already have refurbishment and connection programmes, so it is prudent to assume they can take new connections only from the mid-2030s, and that capacity is not secured until a connection agreement is signed.

Longer term, the Large Energy User Action Plan, published in January 2026 according to A&L Goodbody, sets out 17 actions over five years. It includes Green Energy Parks near renewable generation, a national planning statement due in 2026, support for flexible connections, and a Private Wires Bill, which would allow private ownership of electricity wires in limited circumstances. EirGrid notes its process was written without reference to private wires legislation, which is still being developed.

What is firm and what is uncertain

Firm, because it is published and dated: the decision reference CRU/2025236 and its 12 December 2025 date, EirGrid's Version 3 process and constrained area overview of 20 May 2026, the size bands at 1 MVA and 10 MVA, the 80 percent renewable rule with its six year glidepath, and the CSO consumption series to the end of 2025.

Uncertain: the policy is under legal challenge. EirGrid states that judicial review proceedings have been brought against the regulator over decision CRU/2025236, and that applicants proceeding in the meantime do so at their own risk, since the process may change. A&L Goodbody reports the challenge comes from an environmental group and centres on the proposal that onsite fossil fuels could meet up to 20 percent of energy demand, and that it had not passed the preliminary leave stage at the time of its writing.

Also uncertain: how much capacity outside Dublin is real. EirGrid's 150 to 300 MW figure for the Galway, Limerick and Cork area is a high level desktop assessment, and it warns that many 220 kV substations may only take new connections from the mid 2030s. The 31 percent by 2034 projection depends on contracted demand being used in full. The heat maps EirGrid is to publish, showing demand capacity across the system, were still being prepared when its May 2026 documents appeared. Finally, EirGrid's own page says it awaits clarity from the regulator on how future demand applications, including data centres, are to be processed, so further procedural changes are possible.

The practical effect is that the rules are in force and being used, yet a court outcome could still change them.

What to watch next

• The judicial review. Whether leave is granted, and any ruling on the fossil fuel share, could change the generation requirement.
• EirGrid's demand capacity heat maps and any update to the constrained area overview.
• The national planning statement for data centres that A&L Goodbody says the Large Energy User Action Plan expects in 2026, and progress on the Private Wires Bill.
• The next CSO release on 2026 consumption, which will show whether the 10 percent annual growth seen in 2025 continues.
• The first data centre connection offers issued under Version 3, and whether any are outside greater Dublin.

For the wider European picture, see Europe's data centre power and permitting limits. The Nordic contrast, where cheap power meets fast growing grid queues, is covered in Nordic AI data centres, and the general mechanics of waiting for a grid connection are in the interconnection queue explained.

If you buy cloud or colocation capacity in Ireland, ask whether new capacity sits in the existing Dublin estate or in newly permitted sites, and whether it depends on generation that has not been built. For the software that runs there, Safeguard offers SBOM and dependency scanning, with a free scan at https://gold.safeguard.sh/scan.

Quick check

Sources

• EirGrid, Data Centre Constrained Area Overview, 20 May 2026
• EirGrid, Data Centre Connection Offer Process and Policy Version 3, 20 May 2026
• EirGrid, demand connections page
• Central Statistics Office, Data Centres Metered Electricity Consumption 2025, key findings
• Central Statistics Office, Data Centres Metered Electricity Consumption 2024, key findings
• A&L Goodbody, Data centres and the grid: how recent Irish policy will shape the sector
• Mason Hayes and Curran, Large Energy Users connection policy, 20 February 2025
• Philip Lee, Re-balancing the digital bargain: Ireland's new CRU large energy user connection policy, 22 December 2025
• Eurostat, electricity price statistics

Last reviewed: 19 October 2026.