To support the implementation of the Market-wide Half Hourly Settlement (MHHS) Programme, changes are required to the Electricity Enquiry Service (EES). These changes will be made in alignment with the implementation of the MHHS legal text into the industry codes and when the central systems become live. These EES changes will impact all EES Users.

Changes to EES

The changes to EES include:

• New, amended or removed data items, determined by the MHHS Design
• New user roles to reflect the new and amended market participants
• Moving to an event-driven architecture and near-real-time updates to data
• Reflection of forward and reverse migration between legacy and MHHS arrangements

The changes will impact the GUI/User Portal, the API and reporting. The delivery of the changes is part of the REC MHHS programme.

Further information on what is changing can be found in the EES related documents on the REC MHHS M8 Release wiki page. The changes to the system will go live in line with the M8 release.

Data items during MHHS Transition

During the 18-month period when Metering Points are being migrated into the MHHS arrangements, EES will return data items differently depending on an individual Metering Point’s migration status.
The following data items will be ‘NULL’ for non-MHHS Metering Points:

• Manufacturers Make and Type
• Disconnection Date
• Import/Export MPAN Supplier ID*
• DUoS Tariff ID
• DUoS Tariff ID Effective From Date (EFD)
• Data Service EFD
• Data Service Effective to Date (ETD)*
• Data Service Name*
• Data Service MPID
• Data Service DIP ID
• Metering Service DIP ID
• Assigned MDR EFD
• Assigned MDR MPID
• Assigned MDR DIP ID
• Customer Direct Contract Data Service Flag
• Customer Direct Contract Data Service DIP ID
• Customer Direct Contract Data Service MPID
• Customer Direct Contract Metering Service Flag
• Customer Direct Contract Metering Service DIP ID
• Customer Direct Contract Metering Service MPID
• Annual Consumption
• Annual Consumption EFD
• Annual Consumption Quality Indicator
• Market Segment Indicator
• Market Segment Indicator EFD
• MHHS Indicator
• Distributor DIP ID
• Supplier DIP ID

* Not available in the EES API.

The following data items will be ‘NULL’ for MHHS Metering Points:

• MPAN Designation
• Line Loss Factor Class ID
• Line Loss Factor Class ID EFD
• Measurement Class ID
• Measurement Class ID EFD
• Meter Time Switch Class
• Meter Time Switch Class EFD
• Related MTC
• Data Aggregator MPID
• Data Aggregator MPID EFD
• Data Collector MPID
• Data Collector MPID EFD
• SMETS Version

Amendments to the REC

Through the MHHS code drafting activities, updates are being made to the following REC documents to reflect the changes being made:

• EES Service Definition
• EES API Technical Specification
• Electricity Data Access Matrix

Ahead of the release, the approved documents can be found on the REC MHHS M8 Release wiki page. The changes to the system will go live in line with the M8 release on 22 September 2025.

Frequently Asked Questions

Will the current ‘topline’ data items (Profile Class (PC)/Meter Timeswitch Code (MTC)/Line Loss Factor Class (LLFC)) be populated for MHHS Metering Points?

If a Metering Point is in MHHS arrangements the MTC and LLFC will be null. However, the DUOS Tariff ID will be displayed in place of the LLFC. The Profile Class will be returned, if it is populated.

It should be noted that in MHHS the Profile Class values are mandatory for Traditional meters but optional for Advanced and Smart. For Advanced and Smart the PC populated prior to migration will be carried forward into MHHS and maintained until such time the Supplier decides to remove it.

If a non-MHHS Qualified Supplier is quoting on n MHHS Metering Point, that they will reverse migrate on the Switch, will they be able to view the legacy data items in the API?

No, the API will return the data items according to its status as an MHHS Metering Point.

Will the Standard Settlement Configuration (SSC) be displayed for MHHS Metering Points?

For MHHS Metering Points, the SSC will be returned, if it is populated.

Similarly to the Profile Class, it should be noted that in MHHS the SSC values are mandatory for Traditional meters but optional for Advanced and Smart. For Advanced and Smart the SSC populated prior to migration will be carried forward into MHHS and maintained until such time the Supplier decides to remove it.

When an MHHS Metering Point is reverse migrated, how will the legacy (non-MHHS) data items be populated?

On a Reverse Migration, generally EES will be populated by legacy data items with the last known value of that Metering Point in its non-MHHS state. Please note the Profile Class and Standard Settlement Configuration are not legacy data items.

On a Reverse Migration EES will display the LLFC as populated into MPAS by the relevant Distribution Network Operator (DNO)

When an MHHS Metering Point is reverse migrated, how will the ‘topline’ data items be populated?

All the registration information required to populate the D0217/D0260 flows (including the Profile Class and Meter Timeswitch Code) will be populated by MPRS using the last information held when the Metering Point last traded in legacy arrangements. If the Metering Point did not previously exist in legacy then default values we be used as detailed in the MHHS design. These values will be populated in EES unless updated by the Supplier via a D0205.

If a MHHS Metering Point changes DUoS tariff bands from April 2026, but then reverse migrates is the LLFC reinstated with the M10 frozen value, or updated to reflect the post-Apr 2026 class change?

The LLFC (for legacy) and DUOS Tariff ID (for MHHS) is populated into EES by MPAS. EES will display the value provided by the relevant Distribution Network Operator (DNO).

How will the changes to the data items in the Supply Number be reflected in EES?

EES will display the Supply Number in the GUI/User Portal according to the updated Supply Number Format that was implemented in the Data Specification at M8 via R0083. A supporting document is available which gives additional guidance on population of the data items - R0083 - Guidance for Supply Number population V2.0.

Events relating to EES

The following events have been hosted by RECCo to support users ahead of the changes being made. Recordings, slides and further FAQs are available for each event.

Electricity Enquiry Service (EES), MHHS Live Demo - 15 July 2025

RECCo welcomed around 400 EES users to a live demo exploring upcoming changes to the EES Portal, ahead of MHHS go-live at Milestone 10 (M10).
Hosted by RECCo's MHHS Service Lead, Jonny Moore, the session also covered clarity on Meter Point Administration Number (MPAN) toplines, Customer Direct Contract indicators and the display of Annual Consumption Data.

You can view the recording and supporting documentation here on the RECCo website.

RECCo Webinar: Changes to the Electricity Enquiry Service for MHHS

On 06 July 2023, RECCo hosted a webinar about the upcoming changes. To find a summary of the event, download the slides and watch a recording of the webinar please visit the RECCo website. Frequently asked questions can also be found on this page.