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.

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.

Changes to the BSC

MHHS implementation will require the biggest change to Elexon’s BSC systems and processes in 20 years. We will be changing key parts of our legacy BSC Settlement architecture to ensure that it can cope with the increased data volumes that will be available from smart meters.

We have already started an internal programme which will ensure that these  changes are delivered smoothly, and on time, ready for the transition to MHHS in 2025.

The changes needed to implement MHHS are expected to impact most areas of our business. Some of the most highly impacted areas are:

The process for making changes to the BSC will not be affected by MHHS, However the BSC rules management team will need to complete changes to the code documents to accommodate MHHS.

Our current expectation is that:

  • 19 BSC Sections will be impacted
  • 39 existing Code Subsidiary Documents will be impacted (Balancing and Settlement Code Procedures – BSCPs – and Service Descriptions)
  • 4 new BSCPs will need to be drafted
  • 1 new Service Description to be drafted

Recent Modifications, Change Proposals and Issues

New BSC services to support MHHS

To manage the increase in data volumes from MHHS we will need to develop four new services / systems that will be integrated with our new digital platform, Elexon Kinnect.

The four new systems / services that will be developed are:

  • Load Shaping Service (LSS) which will take on some of the duties that Data Aggregators perform in the BSC currently, by collecting all half hourly consumption data and deriving load shapes from the data which BSC Parties can use to verify any missing or invalid data that they have
  • Market-wide Data Service (MDS) which will take half hourly data from each meter point and aggregate it
  • Volume Allocation Service (VAS) which replaces the volume allocation run that the Supplier Volume Allocation Agent carries out by using aggregated data from the MDS
  • Industry Standing Data (ISD) – a system which will be an enhanced version of the Market Domain Data service with fewer manual process to maintain it


  • 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 – November 2021 – we will run a competitive tender process to select an external vendor (or vendors) to design, build and test the new services and systems explained above
  • November 2021 to the end of Q1 2023 – the vendor will design, build and test the new services and systems collaboratively with the Elexon programme team

Our internal changes will need to be ready by April 2023 to support industry testing which goes through to June 2024.

Following this there will be a transition phase (where legacy systems and process will be running alongside the new services and systems 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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