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Data Centres: Boom and Backlash
8SEP

Ireland codes a 900 MW load-loss limit

2 min read
13:06UTC

EirGrid and SONI issued a grid-fault curtailment procedure to data centres on 30 June, capping instantaneous demand loss at 900 MW to stop synchronised backup-power trips destabilising the grid.

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Key takeaway

Ireland made data-centre curtailment a permanent grid rule, while the US still declares an emergency each time.

EirGrid and SONI, the grid operators for the Republic of Ireland and Northern Ireland, issued a fault-ride-through (FRT) demand-curtailment procedure to affected data-centre customers on Tuesday 30 June, live from July. 1 fault-ride-through is the grid-code requirement that a large load stay connected through a brief voltage dip rather than trip to its own backup generators. Their MPID345 paper set a 900 MW ceiling on how much demand the grid can afford to lose at once, warning that a single fault could otherwise knock more than 1,150 MW of data-centre load offline together.

The physics matches a risk the beat has tracked mostly in America. The US Department of Energy (DOE) used Section 202(c) emergency powers to let PJM, the largest US grid operator, curtail backup-equipped data centres twice in 2026 , and Ireland's energy regulator, the CRU, reopened large-load connections in June even as EirGrid warned of shortfalls .

The two systems reached the same class of ceiling from opposite legal directions. Washington must declare a statutory emergency event by event; Dublin has written a standing grid-code rule that runs on its own. Both treat concentrated data-centre load as a single point of failure the grid must be able to shed, and the build-out is what created that risk.

Deep Analysis

In plain English

Ireland's electricity grid operators, EirGrid and SONI, have told data-centre customers there is now a hard limit on how much power demand can suddenly vanish from the grid at once, for example if a big data centre trips offline during a fault. That limit is 900 megawatts; above roughly 1,150 megawatts of sudden loss, the grid itself could become unstable. This matters because Dublin's data centres already use about half of the region's electricity. The rule does not stop new data centres connecting, but it does mean big campuses now have to prove they will not destabilise the grid if something goes wrong.

Deep Analysis
Root Causes

EirGrid's 900 MW ceiling exists because Ireland's data-centre demand, now about 32% of national electricity against 22% in 2024, grew faster than CRU's 2025 reconnection conditions anticipated; the regulator required 80% renewable supply and full on-site backup from new entrants, but did nothing to cap the instantaneous demand loss a fault at a large Dublin campus could cause across the whole system.

The 1,150 MW imbalance warning is the gap between what EirGrid judges the system can absorb without mitigation and what a cluster of large Dublin sites tripping simultaneously would actually cost; the 900 MW ceiling is the operator drawing a line just below that failure threshold rather than waiting for CRU to write a new connection rule.

Escalation

The procedure is a defensive grid-code measure, not evidence of an imminent shortfall; escalation would be a live curtailment event or a further tightening of the ceiling if Dublin campus growth continues.

What could happen next?
  • Risk

    Operators unable to demonstrate fault-ride-through compliance may face new engineering costs or curtailment exposure even after clearing CRU's 2025 connection conditions.

  • Precedent

    A standing grid-code ceiling, rather than a one-off emergency order, gives European grid operators a template that does not require new legislation to enforce.

Sources:EirGrid / SONI·EirGrid / SONI
Mentions:EirGrid →SONI →Ireland →CRU →Department of Energy →PJM Interconnection →Northern Ireland →Pure DC →Dublin →Chevron →OECD →Section 202(c) →International Energy Agency →Washington →Microsoft →Texas →fault-ride-through →
First Reported In

Update #10 · New York freezes data centres by decree

EirGrid / SONI· 15 Jul 2026
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Causes and effects
Caused by
DOE lets PJM switch off data centres
EirGrid's FRT curtailment procedure parallels DOE's Section 202(c) curtailment authority granted to PJM against the same backup-equipped-load risk.
Occurred 18 May 2026
Read story →
Irish regulators split over data centres
EirGrid's curtailment procedure follows CRU reopening large-load connections in June as EirGrid warned of shortfalls.
Occurred 16 Jun 2026
Read story →
This Event
Ireland codes a 900 MW load-loss limit
Ireland has written data-centre curtailment into standing grid rules, where the US still needs an emergency order each time.
Led to
Ireland writes the grid rules into contracts
EirGrid and SONI's 30 June fault-ride-through curtailment procedure is the operational rule MPID 345 now writes into compliance machinery.
Occurred 29 Jul 2026
Read story →
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