14/07/2026

The CRU is seeking views on supplementary information on Grid Code modification MPID 345 (PDF 17.8 MB) and the impact that the proposed compliance and derogation framework will have on demand customers’ businesses. Further documents are available on the consultation page.

The CRU indicates that when transient faults on the transmission system (causing voltage dips) occur, many data centres automatically and near instantaneously reduce their consumption from the grid and switch to their own temporary back-up power sources, to protect IT systems and processes. EirGrid and SONI (the transmission system operators or “TSOs”) have determined an upper limit for demand loss beyond which system stability is at risk (900 MW).

Grid Code modification

Current and proposed measures to manage this include the Grid Code modification, which would impose requirements on existing and future transmission-connected demand facilities.

  • Fault Ride Through: Demand facilities would be required to remain connected and operate stably during and after any fault disturbance, provided the voltage deviation stays within a defined voltage-against-time profile at the connection point.
  • Rate of Change of Frequency robustness: Demand facilities would be required to remain connected during RoCoF events up to ±1 Hz/s, measured over a rolling 500 milliseconds.
  • Active Power Recovery: Following fault clearance, a demand facility would be required to restore at least 90% of its demand within 500 milliseconds of grid voltage recovering to 90% of nominal voltage. The ramp-up rate would be agreed with the TSO.

The Grid Code modification will come into effect five weeks after the date of CRU approval (“Modification Effective Date”).

Because transmission-connected demand facilities are currently largely not in a position to comply with these requirements, a compliance and derogation framework is proposed.

Compliance and derogation framework

EirGrid sets out three pathways for derogations, which it indicates need to be in place before the Modification Effective Date.

  • Standard process: Applicants must include a plan to achieve compliance with the modification. Applications are assessed by the TSO, which issues a recommendation to the CRU.
  • Group process (data centre): The conditions for group derogations are pre-determined as set out in the framework proposal paper (PDF 1.2 MB). Applicants must provide a compliance plan within three months of the Modification Effective Date and compliance status reports every three months. Derogations would be valid for 24 months.
  • Group process (non-data centre): While similar to the description above at pathway 2, the applicant would have 12 months from the Modification Effective Date to provide a compliance plan.

EirGrid notes that, where a derogation is not in place by the Modification Effective Date, the customer will be non-compliant with the Grid Code and the customer is at increased risk of “demand control”.

Usage cap on data centres

Derogations granted to data centres in the group process would be subject to a Demand Utilisation Threshold (“DUT”). In the standard process, EirGrid could recommend a DUT, which would be subject to CRU approval.

A DUT would set a fixed monthly demand limit (MVA) for “non-compliant demand”. A demand facility would be permitted to exceed the DUT provided that the monthly average non-compliant demand is at or below the DUT; any ‘peaks’ in demand do not exceed the DUT plus 10 percent; and, where the demand facility anticipates a scenario requiring demand to exceed the DUT by more than 10 percent, prior written approval from EirGrid is obtained.

EirGrid’s framework proposal paper (PDF 1.2 MB) states that data centres that can demonstrate full compliance with the Grid Code modification can continue to use demand up to their contractual Maximum Import Capacity.

Proposals include a possibility for the demand facility owner (or parent company) to manage the DUT of each connection agreement on a portfolio basis.

In response to feedback, EirGrid proposes three potential ways of calculating DUT from 2025 highest monthly consumption based on:

  • SCADA data,
  • customer meter data, or
  • the higher of DUT based on each of these data sets.

The consultation papers recognise that use of a DUT will have a cost and an impact on renewables.

EirGrid has also developed a fault ride through demand curtailment procedure, expected to be in use in July 2026, under which it would instruct data centres to curtail demand with a view to EirGrid managing the 900 MW upper limit. The CRU states that the procedure was issued to impacted customers on 30 June 2026.

Next steps

The CRU intends to issue a decision as soon as possible. Given the urgency the CRU has signalled, the Grid Code modification could be in place quickly.

It is unusual to see requirements such as those in the compliance and derogation framework with the potential to impact customer entitlements under connection agreements in this way, and it may serve to strengthen the strategic importance of reliable onsite generation for customers. Customers have been engaging with the development of the compliance and derogation framework and will also need to ensure that any operational impacts are accommodated in service level agreements.

It should also be borne in mind that requirements for the connection and operation of demand facilities are regulated under EU law on the internal market in electricity, including under Commission Regulations establishing a Network Code on Demand Connection and a Guideline on electricity transmission system operation and that, when applying these acts, TSOs and regulatory authorities must apply the principles of proportionality and non-discrimination.