Understanding the bigger picture: What is MHHS?
Market-wide Half Hourly Settlement (MHHS) is a major reform stemming from Ofgem’s Significant Code Review (SCR), designed to modernise electricity settlement. It introduces the Target Operating Model (TOM), which restructures market roles, enhances data processing, and mandates industry-wide compliance to support Great Britain’s transition to a smarter, low-carbon energy system.
What the webinar covered
Hosted by our MHHS Service Lead, Jonny Moore, the session included a live demonstration of the enhanced portal, offering a first look at key updates and how they’ll affect users. The webinar also showcased several service enhancements to the EES Portal, including:
- Migrated MPAN indicator: bringing greater clarity to Meter Point Administration Numbers
- Customer direct contract indicators: improving visibility of direct supply arrangements
- Annual consumption table: providing quicker access to key consumption data
Attendees participated in a live Q&A session, with thoughtful questions on how these changes will impact daily operations and business processes. Many of the questions helped clarify the practical impacts for users ahead of MHHS go-live.
Thank you to everyone who joined.
Take a closer look
- Download the EES Portal Demo Presentation
- Watch the EES Portal Demo Webinar
- Visit the REC MHHS Wiki on the REC Portal (includes user guides and MHHS Data Access Matrix)
- If you have any questions, contact mhhs@retailenergycode.co.uk
- If you need help with EES access or technical support, contact support@candc-uk.com
- Read our previous news articles on REC MHHS training event: insights and next steps and Introducing the EES API Sandbox
Your questions answered
During the session, we hosted dedicated Q&A sessions to ensure that all key topics were covered and that participants had the opportunity to clarify any uncertainties. Here’s a summary of your most important questions and our answers.
Topic: Portal Display / Data Item Format
Q: Are there different icons for migrated, non-migrated, and reverse-migrated?
A: Different icons exist for each MHHS status: migrated = fast forward, non-migrated = pause, reverse-migrated = rewind.
Q: How do I filter for Unmetered Supplies only for MHHS?
A: We’ve not added any changes to the search filter for this. However, we’ll add this to our consideration list for future improvements.
Q: Is an MPAN unmetered if the Market Segment is Unmetered?
A: Yes, Market Segment U = UMS.
Q: Should it be DUoS Tariff ID instead of DUoS?
A: Yes, it’s been described as DUoS in the Portal for formatting/space reasons.
Q: Will the supplier history be lost? Or is this because it’s in a test environment?
A: There’s no change to the supplier history. This isn’t shown in the demo because there’s no supplier history set in the test environment.
Q: Does this show the registration status at the bottom, like we have in ECOES currently?
A: The registration status will continue to be displayed within the Portal.
Q: Did I understand correctly that we can no longer see objections or registrations withdrawn/cancelled?
A: Yes, that’s correct. A failed COS attempt will now be shown as ‘cancelled’, but it will not include details such as whether it was withdrawn or objected to, etc. EES no longer receives this information.
Q: Have we lost the MS/MOP history section? I think I only saw the DS/DC section.
A: There should be no change to how the MS/MOP history is displayed.
Q: What are the possible values for the MHHS Indicator? Are these the same in the UI and the API?
A: Possible values are T = migrated, F = not migrated, or R = reverse migrated. The API will display the single-letter code, while the Portal will show the expanded description.
Q: Will we be able to see when the site was migrated?
A: Yes, there is an effective date allocated to the MHHS Migration Status.
Q: Are the DIP IDs for agents per MPID, or will there be a different DIP ID if it’s a customer contract?
A: The DIP ID is linked to a particular MPID/Role. The Customer Direct Contract flag does not impact the DIP ID for that MPID.
Topic: Topline Update (R0083)
Q: How different is the MPAN to the item that replaces it in EES?
A: The MPAN core (13-digit item) isn’t changing through MHHS. What will change is the MPAN topline, which forms part of the Supply Number. This will move from displaying the Profile Class, Meter Timeswitch Code and Line Loss Factor Id to the Profile Class, Standard Settlement Configuration (SSC) and DUoS Tariff Id / Line Loss Factor Id (for non-migrated). More details can be found in REC Change R0083.
Q: Are the Meters requiring the display to match the MHHS configuration in line with the way the account will be billed, or left on historical metering setups to the NHH configuration?
A: The SSC should be populated as per the metering set-up rather than how the MPAN will be billed. These will often be the same.
Q: We had heard that the SSC could be either three characters or four characters—is that true?
A: The format of the SSC has not changed. It’s defined as having a physical length of four characters. Many SSC values will have a leading zero.
Q: Is the Supply Number now 22 digits?
A: Yes, the top line is now nine digits, with the MPAN Core remaining at 13. See REC Change R0083 for more details.
Topic: Data Items through MHHS Transition
Q: When you say that the Designation will be replaced by the DPI, do you mean that it will no longer be used (as the DPI is a current data item)?
A: Yes, as the DPI will be populated for all MPANs from M10, the MPAN designation will no longer be populated regardless of MHHS migration status.
Q: Will legacy data items be visible for migrated MPANS (but frozen), or will they not be visible at all?
A: Legacy data items not populated in MHHS will be returned as a null value. The expectation is that these will then be removed from the API following MHHS migration.
Q: With the updated values on ESS, are all other fields not mentioned in the new or depreciated fields remaining in use with no other alterations/changes (e.g. Trading Status)?
A: Yes, fields not covered, including the Trading Status, are unaffected.
Q: Will the SSC continue to be available in ECOES even though it isn’t used for settlement purposes under MHHS, and will this be via the GUI and the API? It wasn’t on the list of removed items, and many suppliers use this information as part of their quoting/sales journeys.
A: The SSC will continue to be used within MHHS and, where populated, will be available in both the API and Web Portal. However, for MHHS-migrated MPANs, it’s only mandatory to populate it for Traditional Metering. Suppliers may choose to remove it post-migration for Smart and Advanced Metering types.
Q: If legacy data is no longer shown, how are suppliers able to confirm what SSC an AMR meter must do during a reverse migration? For example, several AMR meters have a preset SSC that’s programmed in, but when they migrate to MHHS, they will no longer display that SSC.
A: The MHHS design allows suppliers to not populate the SSC for smart/advanced meters. It’s recognised that some smart and advanced meters may need the SSC populated to support metering processes. We’re looking to raise an issue to consider this point.
Q: What replaces Measurement class codes?
A: The Measurement Class, which describes whether something is NHH or HH, isn’t required within the MHHS design. The Market Segment will now describe whether a Meter Point is settled within the Smart, Advanced, or Unmetered segment, and the Connection Type will indicate whether a Metering Point is connected to a Whole Current or Current Transformer. For Current Transformer sites, it will also indicate the voltage.
Topic: Customer Direct Contract Flag
Q: Who sets the direct appointment flag—Agent or Supplier?
A: Only the currently appointed agent can set the Direct Contract Flag.
Q: On the supplier agent and direct agent values, will there be any reporting on multiple agents appointed to a single MPAN, for either the supplier or the agent to investigate?
A: No reporting is currently planned for this, although this may be introduced in the future. Note, it’s possible for the appointed agent and the directly appointed agent to be different.
Q: Is the intention still to restrict the Customer Direct Indicator view only to certain participants on individual MPANs–current and potential gaining Suppliers?
A: The Customer Direct Contract flag is restricted to only be viewed by Suppliers.
Q: Will there be a Customer Direct Contract end date shown? Or just an agent?
A: No, the Customer Direct Contract effective to date has been identified as business confidential information and will not be displayed in the Portal or returned via the API.
Q: You mentioned the CDC flag for metering agreements will send a flow to end this with the agent. What if the customer doesn’t sign a new agreement? Is this for the supplier to manage with default/preferred agents?
A: The appointed agent is responsible for maintaining the flag and updating it as required. It will automatically be removed if the effective to date is reached, which can currently be set to a maximum of three years in the future.
Topic: Annual Consumption
Q: Consumption for the last 12 months, taken at what settlement run? In UMS, this can and often does change for weeks and months after a settlement date has passed.
A: The data is provided by the Elexon Market-wide Data Service using the calculations detailed in the MHHS Annual Consumption Method Statement. Simply, this will be updated monthly using the most recent consumption received for the last 12 months.
Q: Will historic AC values be superseded if amended and replaced, or will you only ever see the latest shared value (even if previous values may have changed)?
A: Only the most recent value is set; previous values will not be amended if consumption has been corrected. The EES Portal will show a history of values received, but only the most recent will be used in calculations, etc. and be returned in the API.
Q: What time in the month will Elexon update AC?
A: Metering Points will be scheduled to have their Annual Consumption updated throughout the month.
Q: Will the annual consumption just be available to the current supplier?
A: The Annual Consumption will be made available to a number of Parties as per the MHHS version of the EES Data Access Matrix. This includes Suppliers, Data Services, and TPIs.
Q: Will the HH data be downloadable?
A: This isn’t an existing feature, but we’ll capture it as a possible future improvement.
Q: Will unmetered MHHS consumption data be visible to DNOs/UMSOs?
A: It will be available to DNOs. UMSO isn’t a party currently covered by the Data Access Matrix; we will investigate this point.
Topic: EES API Sandbox
Q: Would it be possible to update the MPAN cores in the sandbox so that they pass checksum validation? Our systems reject all but two of the MPANs due to checksum failures.
A: Unfortunately, due to the manual process required to update data in the Sandbox, we cannot support this. Our qualification team recognises data limitations within the EES Sandbox, and end-to-end testing using EES is not required for MHHS PIT.
Q: How is test data for EES generated and anonymised, especially considering real consumption data is sensitive under MHHS?
A: Dummy data has been used for the EES Sandbox, and the programme has provided this data for the EES SIT Environments.
Q: Can the postcodes of the test data MPANs be edited? Currently, all appear to be the same, returning an error message as it exceeds the threshold.
A: Unfortunately, due to the manual process required to update data in the Sandbox, this isn’t something we can support. Data limitations within the EES Sandbox are recognised by our qualification team, and end-to-end testing using EES is not required for MHHS PIT.
Topic: General Processes
Q: Will the various “Effective From Dates” (EFD) be individually updated from the actual date of the change? You may be aware that certain EFD fields at the moment all get incorrectly updated with the same Supplier changeover date (e.g., a supply appears to have been energised from 1 October 2024 when in fact it was energised years ago. This is a real issue for validating charges and changes to status).
A: In general, these will be updated by the EFD provided when the item updates. The MHHS design has not changed the existing process of some date items defaulting to the Registration Effective from Date following a Change of Supply. This issue is currently being looked at through REC Issue I0247: ‘Effective Dates in EES‘.
Q: Is all the information visible to all participants, even if not appointed at the time of viewing? This might be important if you want to check the EES view of an ongoing Migration.
A: There has been no change in this area. Data items are restricted to certain participants, but this is not dependent on appointment status. Parties will continue to be expected to have customer permission to view specific Metering Points.
Q: Regarding Primary and Secondary UMS MPANs, our understanding is that there are many Logical Disconnections, and secondary MPANs are being aggregated to their Primary MPAN. How is this tracked, and how does the user see this on EES?
A: Now, when a supply is logically disconnected, the manual search simply fails to return a search at all. There have been no updates to EES around this process. Logically disconnected MPANs will continue to be displayed as they are currently.
Q: Is there going to be a means to view areas with excessive numbers of MPANs? I came across one in Liverpool recently, where even filtering down to the street still had too many results.
A: This isn’t an existing feature, but we’ll capture it as a possible future improvement.
Q: Will the export flag remain?
A: Yes, there’s no change in this area.
Q: Will this transformation create an opportunity to revisit Change Proposal R0009, “Introduction of SDEP and EES User Maintenance API,” or is it deemed massively out of scope?
A: It’s out of scope of the MHHS changes.
Topic: MHHS Cut Over
Q: When will the “new” EES API and Portal be available? Will new URL information need to be shared? If so, do we need to check that you have the right contact information for us, or will it be sent to the MHHS principal contact?
A: The updated EES Portal and API will be available from 09.00 on 22 September 2025 (MHHS Milestone M10). There are no changes to the URLs used to access the service, and no action is required from EES users. Communication will be sent to EES Master Admin Users and through the REC Newsletter.
Q: Will the EES User Guides published on the REC Portal be updated to reflect these changes? If so, when will the updated versions be available?
A: The updated EES User Guides are available on the REC Portal.
Q: If updates do not make their way through the system during the cut-off dates, will this create a backlog of updates/changes/requests/flows, etc. that will begin flowing over a few days, or is it a complete stop of all data incoming?
A: As we’d not normally expect updates from MPAS over the weekend, any backlog will be limited to Central Switching Service (CSS) flows. We’ve built in time to process these into the cut-over plan.
Q: Who do we contact for any technical issues during integration with the EES API?
A: Please contact C&C Group at support@candc-uk.com
Q: Will there be any screenshots provided highlighting the location of the amended data locations in the training pack/slides?
A: These screenshots can be seen in the updated User Guides.
