What is CMP470?

CMP470 is a Connection and Use of System Code (CUSC) modification proposal that proposes the introduction of an Oversubscribed Technologies Commitment Fee (OTCF) for certain 'oversubscribed technology' electricity generation projects connecting to the Great Britain transmission or distribution system. This is intended to set a floor on the amount of security these projects are required to provide to NESO in order to obtain a connection. It will also set a floor for the cancellation charge. The modification proposal was raised on 20 March 2026 by Field Energy and has been granted urgent progression status by Ofgem.

Why has CMP470 been proposed?

Following the TMO4+ connections reform package, certain protections introduced by NESO have meant that, for certain technologies, projects that have qualified for Gate 2 offers significantly exceed the Clean Power 2030 (CP30) capacity targets. Battery Energy Storage Systems (BESS) projects are particularly affected by this. Currently around 90GW of operational and Gate 2 BESS capacity exists, against an estimated CP30 requirement of around 29GW by 2035.

In the proposer's view, this excess of projects with Gate 2 offers undermines the objectives of connections reform because NESO and transmission owners are forced to plan network infrastructure for a significant number of projects that will never be built, delaying connections for all technologies.

The proposer notes that in many cases there is insufficient incentive for less viable oversubscribed technology projects to leave the queue, as many projects have very low cancellation charges and security requirements — particularly those using pre-existing substation bays. Generally, the security amounts only become substantial relatively late in the project lifecycle, delaying viability assessments by developers.

Ofgem's provisional assessment is that the current level of oversubscription represents a material defect and that intervention is justified. The key issue for Ofgem is not whether attrition will eventually occur, but whether it occurs sufficiently early to support efficient network development and to reduce the risk of consumers funding infrastructure based on projects that ultimately do not connect.

How the OTCF mechanism would work

CMP470 proposes a cancellation charge securities and liabilities floor mechanism through the OTCF, which would operate broadly as follows:

  • Activation threshold: The OTCF is triggered when total operational and Gate 2 capacity for a technology exceeds the relevant capacity target by more than 50%, provided the relevant capacity target exceeds 5GW.
  • Initial floor: Set at £3,000/MW upon first activation, for the first six-monthly period.
  • Escalation: If oversubscription does not reduce by at least 25% in each subsequent six-monthly period, the floor increases initially to £5,000/MW and thereafter in £5,000/MW increments until the floor reaches a cap of £25,000/MW.
  • De-activation: The OTCF is disapplied once oversubscription falls below 25%.
  • Application: The OTCF applies to all projects of the relevant oversubscribed technology with a Gate 2 offer, up until energisation, including co-located projects (although there will be an exemption for co-located projects where the oversubscribed technology connects after the other technology, does not increase the Transmission Entry Capacity and has minimal network impact).

The OTCF would be applied through the existing 'Cancellation Charge'/'Cancellation Charge Secured Amount' framework. Where a project's Cancellation Charge or Cancellation Charge Secured Amount falls below the relevant OTCF level, the amount below the floor would be increased to the applicable minimum level through the biannual cancellation charge process. As is already the case, securities posted are returned where a project proceeds to connection.

Ofgem's minded-to position is to approve the proposed solution set out above. However, it has not made its final decision.

The CMP470 workgroup also developed several alternative proposals, although Ofgem's minded-to position is not to pursue any of these further.

Consultation and Implementation Timeline

The CMP470 workgroup issued its draft final modification report to the CUSC panel on 6 July 2026, followed by the final modification report being issued to Ofgem on 14 July 2026. Ofgem's minded-to consultation document was published on 17 September 2026, and the consultation was open until 1 October 2026. Ofgem's final decision will follow the consultation.

If approved, CMP470 would be implemented into the CUSC 10 business days after Ofgem's final decision. However, the OTCF would not be activated until a sufficiently complete and stable view of the reformed connections queue is available, following completion of the G2tWQ process and the first CMP434 Gated Application Window. Under the current implementation assumptions, the OTCF would first be reflected in the July 2027 securities statement, with any resulting securities becoming payable from October 2027.

Implications for BESS and other developers

If approved by Ofgem, the modification will directly impact developers of projects that receive and accept Gate 2 offers for technologies oversubscribed relative to the capacity targets in the CP30 Action Plan, potentially exposing them to higher cancellation charges and security obligations. It is initially expected to apply only to BESS developers, as currently this is the only technology where the oversubscription threshold is expected to be met.

Further details regarding CMP470 can be found on NESO's dedicated webpage. Details of the Ofgem minded-to consultation are available on Ofgem's website.

How we can help

Our Energy team is closely monitoring CMP470 and its potential impact on developers with projects in the connections queue. If you have questions about how this modification may affect your project, please get in touch with Gus Wood, James Stanier, George Nixon or Katherine Huet.