This page provides full details of the proposed change, relevant dates and decisions.

What is the issue?

CM Rules prohibit a change in Capacity Market Unit (CMU) configuration after Prequalification. This prevents Agreement holders from changing CMUs to reflect changes in project development and/or commercial structures. This may limit the commercial flexibility of Agreement holders, increasing the risk of project non-delivery, preventing more efficient commercial structures, and ultimately increasing Capacity Market costs.

What is the proposed solution?

Amendment to the CM Rules to allow CMUs to be merged after Prequalification subject to the total Connection Capacity and Generating Technology Class of each component (and therefore De-rated Capacity) being unchanged.

Title Decoration

Diagram of CMAG Rule Change Proposal stages: Submission, Scheduled, CMAG development, Consultation, With Ofgem, Implemented.

CMAG development phase

This is the stage after the CMAG has initially considered the CM Rule Change Proposal and has determined that further assessment is required of the proposal. Activities in this stage may include the development  of possible solution options, the development of legal text for a proposal and/or the consideration of the impacts of a solution on relevant stakeholders.

Proposer: Waters Wye Associates Type of change: Amendment Date Raised: 15 November 2023 Category: Assurance

Next Steps
Title Decoration

Milestone Date
Proposal Form Submission 8 November 2023
CMAG Initial Consideration Meeting 14 (23 November 2023)
CMAG Development Meeting 15 (13 December 2023)
CMAG Recommendation to Ofgem Meeting 15 (13 December 2023)
Ofgem Statutory Consultation TBC
Implementation TBC

Impacts and Related Changes
Title Decoration


Capacity Market Rules Sections

  • Rule 4.4.4 – Configuration of Generating Units

Impacted Parties

  • Capacity Providers
  • EMR Delivery Body
  • CM Settlement Body

Related Changes

CP374 ‘Splitting Capacity Market Units’

Title Decoration

CP375 Merging CMUs Proposal Form v1.0

Contact information
Title Decoration

Lead Analyst:
Chris Arnold, Senior Change Lead: Capacity Market
[email protected], 020 7380 4221