CRU Decision on MEC Sharing: A New Pathway for Co-located Renewables and Storage

Co-located units may now use one export limit flexibly, but the combined export must never exceed the site MEC and the site must have controls and sub metering to ensure compliance. Previously, adding a second technology typically required a separate MEC application under the Electricity Connection Policy- Generation and System Services (ECP-GSS) process. The new approach aims to optimise existing infrastructure and accelerate renewable integration.

Project types: Hybrid Co-located versus Integrated Hybrid

The Decision distinguished between two project types.

A Hybrid Co-located Project combines multiple generation and/or storage technologies behind one connection point, with each unit separately sub metered and registered, operating independently for market, settlement and dispatch; this category is eligible to share a single MEC.

An Integrated Hybrid Project also combines multiple technologies behind one connection, but the units are registered and operated as a single market unit; this model is out of scope because it would require extensive market, code and systems changes, though the CRU notes potential future merit. The policy is technology neutral but remains subject to technical studies and code compliance.

The Decision applies only to single entity sites at this stage, with multi entity rules to follow.

Operation and Modifications

Each technology continues to participate in the Single Electricity Market as a separate unit, so Availability Declarations, Physical Notifications, Dispatch and System services commitments must be coordinated to ensure the aggregate never breaches the site MEC. 

The CRU has asked the system operators to bring forward targeted code and system updates across market arrangements, balancing market settlement, system services and compliance so hybrids are treated coherently. Where no MEC increase is needed, developers should use the Modifications to Generation Connection Offers process; where an increase or a new connection is sought, the ECP-GSS process applies.

The Decision notes that sharing MEC between synchronous conventional units and Power Park Modules may require further technical and regulatory development before it can be accommodated.

The Decision flags that adding a non-Priority Dispatch unit (such as a battery) to an existing Priority Dispatch renewable unit is likely to be treated as a "significant modification" under SEM 20 072, resulting in the loss of Priority Dispatch status for the existing unit. The TSO has indicated that mixed Priority Dispatch and non-Priority Dispatch configurations behind a shared MEC are not currently feasible, meaning MEC sharing can only be implemented for units under non-Priority Dispatch at this time. The CRU has indicated that further assessment is needed and the system operators should revisit solutions for mixed configurations as implementation progresses.

The CRU’s April 2025 Consultation Paper (CRU202528) asked for comment as to whether a pilot MEC sharing programme (suggested by the TSO/DSO) should be run prior to full implementation?

Under the Decision the CRU decided not to implement a pilot, agreeing with the broad stakeholder view that pilots are unnecessary for what are well-established technologies with sufficient international experience, and that a pilot could introduce avoidable delays.

Potential Gaps

Energy sharing (cross charging between co-located RES-E and BESS) is not permitted and is deferred for further consideration due to the wide ranging changes it would require across dispatch, metering, settlement and market design. Multi entity configurations, where multiple legal entities sit behind a single connection point, are also out of scope and will follow legislation under the Government's Private Wires Bill and a separate CRU workstream; until then, projects must use a single legal entity to access MEC sharing. The CRU has acknowledged it will engage with the system operators to explore energy sharing behind the meter, signalling this is an active area of future work rather than a closed door.

Also highlighted by the stakeholders to the CRU, it will be interesting to monitor how the hybrid co-located model functions from the perspective of revenue certainty. Each unit must participate independently in the market, with coordinated availability declarations and physical notifications that must remain within the site MEC at all times. This will test, administratively and operationally, the extent to which dispatch can be optimised dynamically across different technologies particularly in scenarios where, commercially, a developer might wish to move energy between co-located assets to manage curtailment. 

Also from a project marketability perspective, it will be interesting to see how the full revenue potential value of co-location (including curtailment mitigation, optimised dispatch, and participation in emerging products such as 24/7 hourly matching or baseload-style products) is modelled into the requirement that hybrid projects must operate as separate market units rather than as a single integrated unit.

Next Steps

The system operators will publish an Implementation Roadmap with activities and timelines and will provide quarterly public progress updates; the CRU will monitor delivery and seek acceleration where possible. Developers can now plan co-located hybrids under one MEC if they remain within the export cap and install compliant controls and sub metering, using Modifications where no MEC increase is needed or ECP-GSS where an increase or a new connection is sought.

Conclusion

The Decision enables the deployment of hybrid projects by allowing co-located technologies to share one contracted MEC at a single connection point. We can expect net benefits from MEC sharing through increased renewable output at existing connection points, shorter delivery timelines, reduced need for reinforcement, and improved system flexibility, which should support consumer value.

Further policy development will be needed to ensure MEC sharing can be used to its full potential and to realise the full system-wide benefits that hybrids can deliver. In the meantime, the decision should support a more efficient, flexible and faster deployment of renewable generation and storage, helping to advance Ireland's transition to a low carbon energy system.

This article has been contributed to by Seán Scally (Partner), Pranav Nanda (Of Counsel) and Cal Lynn (Associate) in Dublin.