Market-wide Half Hourly Settlement and the BSC


On this page you can find out about what Elexon is doing to ensure that Market-wide Half-Hourly Settlement (MHHS) is implemented smoothly across the Balancing and Settlement Code Central Systems.

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How it relates to you

MHHS is one of the biggest changes to energy markets since retail competition was introduced in the late 1990s.

Elexon has been appointed by Ofgem as the MHHS Programme Manager. This role will involve managing the activity of around 180 organisations across the energy sector to implement MHHS. The programme is due to complete by October 2025.

The implementation activities will be separated from Elexon’s other BSC activities. This ensures that the programme is independent of Elexon.

Guidance for the industry on the MHHS programme

The MHHS programme has a dedicated website that outlines the plans, events and outcomes of the programme.

MHHS at Elexon: The Helix Programme

In 2021, we began the Helix Programme to re-develop BSC Central Systems to support MHHS, and to re-engineer the accompanying processes and procedures which unlock the benefits of MHHS for Suppliers. 

This re-development is needed so that Central Systems can manage an exponential increase in the amount of half hourly data we will need to process once MHHS is implemented in October 2025.  The Helix Programme is the separate from the ring-fenced MHHS Programme Manager role.

The Programme impacts almost all areas of Elexon, with a requirement for transformation of a
number of existing services. Those which are most affected are:

  • Settlement and Invoicing
  • Participant Management
  • Rules Management and Assurance.

Our current expectation is that:

  • 19 BSC Sections and 39 existing Code Subsidiary Documents will be impacted
  • Four new Balancing and Settlement Code Procedures (BSCPs) will need to be drafted (The BSCPs set out procedures that BSC Parties, including their Agents and Elexon, must follow for compliance
  • One new Service Description will need to be drafted (BSC Service Descriptions describe the service to be provided by the BSC Agents).

Recent Modifications, Change Proposals and Issues

New BSC services to support MHHS

MHHS will require the creation of three new services and one new system. The new services were specified in the Ofgem-approved MHHS Target Operating Model. The TOM explains the set of services and Settlement arrangements required to deliver MHHS.  The new systems and the new service will be developed on our new cloud platform Elexon Kinnect.

The three new systems to be developed are:

  • The Load Shaping Service which will calculate energy consumption and load shapes using validated actual Settlement Period level data. These robust consumption profiles will improve the information we provide Suppliers by enabling them to better predict their customers’ usage, and perform their associated balancing activities
  • Market-wide Data Service which will aggregate data for smart, non-smart, advanced and unmetered supplies for Imbalance Settlement and other purposes such as network charges and flexibility offerings. It will also calculate and apply Distribution Line Loss values to the data, enabling it to provide data for BSC Assurance purposes
  • Volume Allocation Service (VAS) which will use data from the MDS to calculate energy volumes for Balancing Mechanism Units. The VAS will replace the legacy Supplier Volume Allocation Agent (SVAA) The VAS feeds into shorter Settlement run times, allowing Suppliers to better manage their credit positions, and pass savings on to customers.

The new system to be developed is:

  • Industry Standing Data – a system which will be an enhanced version of our Market Domain Data and Line Loss Factor services, but with fewer manual processes to maintain it. This will save both time and resources for BSC Parties and Elexon colleagues.


  • May and June 2021 – We carried out internal impact assessments on our processes to discover which areas of Elexon would be most impacted by these changes
  • August 2021 – December 2021 – we ran a competitive tender process to select external vendors to design, build and test the Helix solutions explained above
  • During 2022/23 we will work with the vendors to develop the Helix solutions
  • April 2023 – June 2024 – during this period industry testing of the new solutions will be carried out
  • Post June 2024 – Following industry testing there will be a transition phase where legacy systems and process will be running alongside the solutions before go live of MHHS across the industry from October 2025.

Background information

In 2017, energy regulator Ofgem announced a review on whether the whole electricity market (commercial as well as residential properties) should move to half-hourly Settlement. Ofgem’s consultation on its draft Impact Assessment identified the need for a delivery Market-wide Half Hourly Settlement Programme Manager, accountable to Ofgem for ensuring the successful implementation of MHHS.


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