The Commission for Regulation of Utilities (CRU) has approved Modification MPID 345, introducing fault ride-through requirements for existing and future transmission connected demand facilities. It has also endorsed a Compliance and Derogation Framework (CDF) setting out how facilities that cannot meet the requirements immediately may work towards compliance.
Fault ride-through refers to a facility’s ability to remain connected during a short disturbance on the electricity network. Generators already face requirements of this kind. MPID 345 introduces requirements for large demand facilities covering fault ride-through, rate of change of frequency and active power recovery following a fault.
The CRU’s decision follows EirGrid’s assessment of the risk that substantial amounts of demand, particularly data centre demand, could reduce simultaneously during a network fault. A sudden loss of demand can cause a sharp rise in system frequency. If sufficiently large, it could trigger further disconnections and threaten the stability of the all-island electricity system. EirGrid has introduced operational measures to manage that risk, including restrictions affecting interconnector exports, battery charging and the level of renewable generation accommodated on the system.
Which facilities are affected?
MPID 345 applies to transmission connected demand facilities, including data centres and other large demand users. It is not confined to data centres, although the CDF distinguishes between data centre and non-data-centre facilities. The CRU says this distinction reflects differences in their observed response to faults and risks identified through EirGrid’s modelling.
Distribution connected facilities are not covered by MPID 345. The CRU notes that ESB Network intends to propose a related modification to the Distribution Code.
Compliance and derogations
The modification will take effect on 27 October 2026 (five weeks after the CRU’s decision of 22 September 2026). The CRU acknowledges that most affected facilities will be unable to comply immediately. It expects those facilities to report their non-compliance and request a derogation from EirGrid before the effective date.
Under the amended framework, data centre facilities will have six months to submit compliance plans under either the group or standard derogation process, while non-data-centre facilities will have 12 months. The group process is a streamlined route for assessing derogation applications; it does not mean that a company can combine the demand allowances of different sites. Under the group derogation process, EirGrid originally proposed a two-year derogation for both data centres and other demand facilities using that process. The CRU’s decision has extended the period for non-data-centre facilities to five years while the two-year period remains for data centres.
Demand utilisation thresholds may apply to facilities operating under derogations. These thresholds could limit the amount of demand a facility can draw while it works towards compliance. The CRU has decided that meter data will be used to calculate and monitor these thresholds.
The CRU rejected a separate portfolio approach proposed by EirGrid. This would have allowed thresholds to be averaged or reallocated between facilities wholly owned by a parent company. The CRU accepted concerns that this could weaken the incentive for every site to become compliant and could concentrate non-compliant demand in ways that increase system risk.
CRU recognises that the requirements and any associated thresholds may have material effects on individual facilities’ operations. The extent of those effects will depend on each facility’s circumstances and the terms of its derogation.
Wider system impacts and next steps
The decision paper also examines the effects of the measures EirGrid is currently using to manage fault ride-through risk. The CRU notes concerns raised about renewable dispatch down and imperfections costs, restrictions on battery charging and interconnector exports, and delays to operational changes intended to accommodate more renewable generation. Table 1 presents a summary of the main impacts identified in the decision paper.
Table 1: Potential impacts of current operational measures to address FRT risk
| Operational measure or delay | Potential impact |
| Limits on interconnector exports | Reduced trading opportunities and possible difficulty for interconnectors in delivering contracted capacity; countertrading can add to imperfections costs. |
| Higher reserve and inertia requirements | Additional system services costs and changes to which units must operate. |
| Restrictions on battery charging | Reduced operational and commercial flexibility for storage assets. |
| Limits on non-synchronous generation and delayed SNSP trials | More renewable dispatch down and slower progress towards accommodating higher levels of wind and solar generation. |
| Delayed work to reduce the minimum number of conventional units online (MUON) | Continued renewable curtailment. The CRU notes that MUON was the largest driver of renewable curtailment in Ireland in 2025. |
| More stringent frequency control requirements for wind and solar | Additional operational costs for affected generators. |
Approval of MPID 345 will not, by itself, remove those measures. The CRU states that it is currently unclear how long facilities will take to become compliant or what level of compliance will allow EirGrid to begin reducing constraints.
The CRU has therefore directed EirGrid to develop a roadmap for reducing and removing the operational measures, improve its assessment of their costs, and provide updates on compliance and system modelling. EirGrid must report to the CRU quarterly, with the first report due by the end of December 2026. It must also establish a technical working group to address implementation issues, with an initial meeting expected in November.
EAI previously raised concerns about the proposed requirements. We acknowledged the fault ride-through risk but questioned whether the obligations were appropriate for all affected demand facilities, particularly where they would apply to existing sites. We called for fuller industry consultation and an assessment of technical feasibility, costs and benefits and also asked that potential alternatives, including system services and solutions behind the meter, be considered.
The compliance and derogation framework provides time for affected facilities to work towards compliance, but the decision retains requirements for existing facilities and was made without a formal cost–benefit analysis. EAI will monitor how the framework operates in practice, its effects on affected facilities and investment, and whether progress towards compliance enables EirGrid to reduce the measures affecting the wider electricity system.
Source: CRU, Grid Code Modification MPID 345 and Compliance and Derogation Framework Decision Paper (CRU2026145), published 22 September 2026.