There has never been a legal moratorium on data centres in Ireland. The CRU rejected one in November 2021 (CRU/21/124), but its connection criteria and EirGrid's January 2022 statement that Dublin could take no new connections until about 2028 worked as a de facto pause. The CRU's December 2025 decision replaced it with a bring-your-own-power route.
From open door to moratorium to 'bring your own power'
The de facto moratorium stopped new grid contracts from Nov 2021, but data centres' share of electricity kept climbing, from 14.1% in 2021 to 23.2% in 2025, as sites contracted earlier were built out.
The top panel draws each policy phase to scale behind the CSO's yearly figure for data centres' share of metered electricity, which rose from 5% in 2015 to 23.2% in 2025. The moratorium was never a law: it was the CRU's November 2021 direction plus EirGrid's Dublin pause, under which only one new data centre was contracted by mid-2025. The CRU's December 2025 decision replaced it with a demanding route, and in 2026 a new constraint appeared: the grid's limit on how much demand it can lose in a fault, answered by the MPID 345 ride-through rule. Energy parks after 2030 are announced, not built.
In a voltage dip data centres can drop off the grid in milliseconds. EirGrid plans for a worst case in which 90% of their demand goes at once (recorded faults dropped 16–52%), so about 1,000 MW of data centres fills the 900 MW limit, and that happened in Jun 2026.
When a fault dips the voltage, data centres protect their servers by switching to on-site batteries and generators, so their demand can vanish from the grid in milliseconds and frequency jumps. EirGrid's weekly operating rules cap the demand and exports the system can lose in one event at 900 MW; planning for 90% of data-centre demand at risk, roughly 1,000 MW of data centres uses it all, and EirGrid told the CRU that peak was reached in late June 2026. To stay inside the limit EirGrid keeps more spinning plant on (inertia floor 28,000 MWs), caps the instantaneous share of wind, solar, batteries and HVDC imports (SNSP) at 75%, limits battery charging and cuts interconnector exports. The step sketches are schematic, not measured traces.
Estimate"A 100 MW campus adds about 90 MW" is our arithmetic with EirGrid's 90% assumption.
The fix: ride through faults, or accept a cap, until about October 2028
From 27 Oct 2026 every transmission-connected data centre must stay on through grid faults. Most can't yet, so each gets a capped allowance of non-compliant demand until about 27 Oct 2028, and the 900 MW limit itself stays.
The CRU approved Grid Code modification MPID 345 on 22 Sep 2026; it takes effect on 27 Oct 2026 and applies to all current and future transmission-connected demand, data centre or not. A compliant site must stay connected through a fault, withstand frequency changes of ±1 Hz/s and recover 90% of its demand within 500 milliseconds. Existing data centres get a 24-month group derogation, with a compliance plan due within six months, and meanwhile each has a Demand Utilisation Threshold (DUT) capping its non-compliant demand. The caps are sized from the load-rejection limit, but EirGrid has not published the demand loss factor, the allowances or any site's DUT; distribution-connected sites wait for an ESB Networks code change that is not yet public.
EstimateCompliance-plan and derogation-end dates are our arithmetic from the effective date (+6 and +24 months).
In practice a near-moratorium in Dublin: almost all subsequent growth came from capacity contracted before the direction, and EirGrid reported only one new data centre contracted under these criteria by its June 2025 data freeze. Gas-fired on-site generation (to be hydrogen/biomethane-ready) became the expected route; units over 10 MW fall under secondary-fuel and capacity-market rules.
Turned the CRU criteria into an explicit Dublin pause; pipeline projects not yet contracted were stranded or moved toward gas, private wires or regional sites.
Became the reference for planning authorities, the CRU and GNI: GNI stopped contracting new data-centre gas connections beyond the 11 already contracted; councils began citing the principles; the CRU's later 80% renewable requirement draws on 'renewables additionality'.
Shows the mechanism: DCCOPP flexible demand plus CRU/21/124 pushed hyperscalers to on-site gas; contracts signed before the July 2022 pause still proceed.
Shift from 'back-up for yourself' to 'bring new capacity for the system'; emissions requirements dropped to reporting only (later reversed in the final decision).
Ended the open-ended near-moratorium with a defined, demanding route: a data centre now comes as a package of demand plus a gas plant (or storage) plus new wind/solar PPAs. No change for gas connections; an interruptible gas product is to be consulted on separately. SOs had to publish processes by 31 March 2026.
Shifts the long-term answer from 'connect where the grid is' to 'build the grid and generation where the user will be', but mostly post-2030. Widely reported as ending the Dublin 'ban', though the electricity constraint is unchanged.
2026-03-10
Friends of the Irish Environment, Friends of the Earth Ireland, ClientEarth
The door reopened on paper but the map is small: perhaps 150-300 MW nationally outside Dublin versus about 6 GW of expressed interest. In Dublin the required on-site gas generation itself worsens short-circuit levels, so the policy cannot work there until 400 kV reinforcement.
Proposal only (consultation closed August 2026; no decision as of early September 2026). If adopted, data-centre gas becomes non-firm unless it is a market generator, reinforcing the LEU design.
Read from the primary documents. Full timeline on the policy page.
Capacity contracted before the rules changed
38–46%
Of contracted grid capacity actually used, 2025
875 MW average vs 2,000–2,400 MVA
1–1.4 GW
Unused capacity already contracted
growth needing no new contract
1,948 MVA
Protected when the 2021 rules came in
1,884 MVA of it in Dublin
1
New data-centre contract under the 2021 rules
EirGrid
The moat the rules created. Freezing new connections protected whoever already held contracts. They are using well under half of what they hold, so existing operators can roughly double their draw while newcomers wait.
Unused capacity we can tie to named sites (MW)
Amazon (AWS) Cruiserath151
Microsoft Huntstown150
Meta Clonee45
Amazon (AWS) Belgard, Tallaght37
Only Amazon Cruiserath publishes both a contract (240 MVA, 2017) and its 2025 draw. Others compare draw with demand stated in planning or EPA papers, which is not a contract. Average draw understates peak use. MVA converted at power factor 0.95.
EirGrid AIRAA 2026–35 and Constrained Area Overview (May 2026) · CRU/21/124 · EPA annual reports · CSO · quotes checked · as of 2026-10-03
Questions people ask
Did data centres stop growing after 2021?
No. Data-centre electricity use kept rising, to 7.7 TWh in 2025 (+9.9% on 2024, CSO), as existing sites filled capacity contracted before the rules changed.