Market Half Hourly Settlement (MHHS) – Code Freeze Impact

The MHHS Programme was established to deliver the aims of the Electricity Settlement Reform Significant Code Review (SCR). When an SCR is in effect there are rules in place to prevent any Change Proposals which may impact the scope or delivery of the SCR. The MHHS programme has now implemented a Change Freeze to manage this requirement.

There are two freezes within the MHHS Programme.

Change Freeze effective from 6th December 2023. This prevents any changes to MHHS Design or Code Drafting except in the case of fixing defects or supporting the implementation of urgent change.

Core Systems Code Freeze effective from November 2024. This technical freeze prevents any changes to MHHS Central systems and impacts:

• Central Switching Service (CSS)
• Electricity Retail Data Service (ERDS)
• Electricity Enquiry Service (EES)
• And consequential changes to the Secure Data Exchange Service (SDES)

How this impacts the REC

The REC Code Manager is assessing all changes that are already in flight or are to be raised to identify any impact on the MHHS Programme.

• If a REC Change Proposal (CP) requires change to the MHHS design or code drafting, it may have its implementation and/or progression postponed until MHHS Programme Milestone M10 has been completed (target date March – June 2025).
• If a CP impacts MHHS Qualification or Migration, it may be delayed until MHHS Programme Migration Milestone M15 is completed (October 2026)
• Any CP or Data Access requests requiring an amendment to an impacted technical system including changes to API or reporting may be delayed until MHHS Programme Milestone M10 has been completed (target date March – June 2025).