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

What is the issue?

The 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 can 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?

Amend the CM Rules to allow CMUs to be split after Prequalification subject to the total Connection Capacity and Generating Technology Class (and therefore De-rated Capacity) being unchanged. Any Agreements awarded to the CMU would also be split pro-rata to the split of total Connection Capacity between the new CMUs.

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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
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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
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Capacity Market Rules Sections

  • Rule 4.4.4 – Configuration of Generating Units

Impacted Parties

  • Capacity Providers
  • EMR Delivery Body
  • CM Settlement Body

Related Changes

CP375 ‘Merging Capacity Market Units’

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CP374 Splitting CMUs Proposal Form v1.0

Contact information
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Lead Analyst:
Amy Stackhouse, Senior Change Lead: Capacity Market
[email protected], 020 7380 4221