Market-wide Half-Hourly Settlement (MHHS) FAQs

Settlement is the term given to reconciling the difference between the volume of electricity a supplier has 'contractually' purchased and the actual volume used by its customers.

Summer 2024 – industry testing started  to ensure each supplier and meter agent has systems and processes in place that will operate with the new MHHS industry architecture.

If your portfolio includes Unmetered Supplies (UMS) that don’t have a Half-Hourly (HH) meter attached – for example, the electricity that powers traffic lights, streetlights or CCTV - this will be covered by an industry modification designed to support MHHS called P434. All businesses with existing Non-Half Hourly (NHH) UMS will be migrated by September 2025.

September 2025 – on 22 September 2025, MHHS went live and industry code changes came into effect, including changes to the top-line of Meter Point Administration Numbers (MPANs).

October 2025 – the migration window opened for suppliers and agents who had completed and qualified via the  Systems Integration Testing (SIT) route. Due to the scale of the project, customer meter migrations will be phased through 2025, 2026 and into 2027. When your business migrates will depend on when your energy supplier qualifies.

May 2026 – the migration window opens for suppliers and agents who’d chosen the ‘qualification’ route, whereby their systems and processes have been assessed to comply with new MHHS requirements. As before, when your business migrates will depend on when your energy supplier qualifies.

May 2027 – deadline for meter migrations to the new MHHS system are to be completed.

July 2027 – the new MHHS model will come fully into effect.

The MHHS programme will significantly transform various industry processes related how suppliers reconcile, or settle, the difference between the volume of electricity they have purchased and the actual volume used by its customers.

This new operating model will create a segmented electricity market based on meter types, with new meter segments replacing existing ones. Additionally, new metering services will be introduced.

Suppliers will need to adapt to the new MHHS requirements and processes. They will also be required to complete qualification processes to demonstrate their ability to continue supplying electricity to consumers. This includes implementing systems and processes that are capable of managing larger volumes of data and collaborating with the new meter agent roles.

Please note that although the commercial impact of MHHS is being assessed, we are not aware of any changes in the gas sector. If this changes, or if another programme is initiated, we will be in touch and will keep all affected customers up to date.

The qualification phase of the MHHS programme has been designed to make sure that we, and all other suppliers intending to operate in the post-MHHS world, have the right systems, processes and controls in place to undertake the Balancing & Settlement Code (BSC) and Retail Energy Code (REC) requirements.

We are happy to confirm that we have qualified in the Advanced Data and Metering Services roles:

• Advanced Data Service (ADS) – this is the service that retrieves and processes settlement period level data (the consumption or export meter data) from advanced meters that are in the Advanced Market Segment.

• The Metering Service (Advanced) (MSA) - this is the service that will be responsible for the installation and maintenance of meters in the Advanced Market Segment

If you have already partnered with third-party metering agents (Metering Service Smart (MSS)/or Metering Service Advanced (MSA) and Smart Data Service (SDS) or Advanced Data Services (ASA) – independently, and we're your supplier, please let us know so we can work with them. 

If you haven't chosen any data or metering agents yet, we will appoint these on your behalf, although they may not be your preferred choice. If you have a preference, it's important to communicate this with us so we can ensure the contracts meet both your requirements and ours.

Our team of experts is dedicated to ensuring that our systems operate seamlessly during and after the MHHS programme. As a result, there should be no downtime or interruptions to your service.

While most changes will occur behind the scenes, we are confident that consumer experiences will be improved based on your meter type and the services you select. We may ask you to confirm information regarding your meters and supply points to ensure accuracy. Additionally, if a meter is not functioning correctly or if we are unable to collect your data remotely, we may need to coordinate with your current Meter Operator (MOP).

Renewing a metering and/or supply contract is not directly tied to the MHHS programme, so it will depend on when your contract is up for renewal and the specific Terms and Conditions (T&Cs) associated with it.

MHHS will not change how any existing Half-Hourly (HH) or Non-Half Hourly (NHH) meters are configured.

If you have a HH, Automated Meter Reading (AMR) meter - or a  Smart meter, which we can communicate with, we will make any changes remotely.

If we are unable to communicate with your meter, we may need to arrange for an agent acting on our behalf to visit your property to update your meter with the appropriate software.

Yes, but this is no different to how energy contracts work at the moment. All meters have a Meter Operator (MOP) and Data Collector (DC) appointed today and charges are usually made directly or through the standing charge in your invoices, depending on your contract and supplier.

For more information on how MHHS will impact MOPs and DCs, please refer to our 'How will MHHS affect third party metering agents (Meter Operators (MOPs) and Data Collectors (DCs))?' FAQ.

All electricity meters will be migrated as part of the MHHS programme. This is unlikely to involve a physical meter exchange - but if any change is necessary, we will let you know in advance.

Our migration schedule will be dependent on several factors, such as how many Meter Point Administration Numbers (MPANs) we are allowed to migrate in a day or the type of meter to be migrated. When the time is right, we will get in touch with our customers to make sure you are kept up to date. As this change will mean all meters will be migrated regardless of type, we will include a list of all the affected meters when appropriate.

If you already have an Automated Meter Reading (AMR) meter, you will transition into the Advanced segment. You will be required to appoint an Advanced Data Service (ADS) agent and a Metering Service (Advanced) (MSA) agent (we can do this on your behalf).

If you have a Smart meter or a traditional 'dumb' meter that operates on a Non-Half Hourly (NHH) basis, you will move into the Smart segment. If this applies to you, you will need to:

If you have a Smart meter or a traditional 'dumb' meter that operates on a Non-Half Hourly (NHH) basis, you will move into the Smart segment. If this applies to you, you will need to:

1. Appoint a Smart Data Service (SDS) agent and a Metering Service (Smart) (MSS) agent. If you don’t manage to arrange this, we will appoint one on your behalf.

2. Continue to provide your meter readings, either online via Dashboard or by getting in touch with us.

 If you would like to arrange a meter exchange to either an AMR or Smart meter, please get in touch. 

If you have an Automated Meter Reading (AMR) or Smart meter and your meter is outside of signal range, or if you have a traditional ('dumb') meter, your meter(s) will still work after you have been migrated and your data and usage will continue to be read monthly or quarterly by agents working on our behalf.

If you would like to arrange a meter exchange from a traditional meter to either an AMR or Smart meter, please get in touch.

All electricity meters will be migrated as part of the MHHS programme. However, in most cases, this won't require a physical meter exchange. If you have a traditional ('dumb') meter, it will still work after you have been migrated and your data and usage will continue to be read monthly or quarterly by agents working on our behalf.

If you would like to arrange a meter exchange from a traditional meter to either an Automated Meter Reading (AMR) or Smart meter, please get in touch.

There will be major changes to existing metering services, with new roles to reflect the new services needed to deliver MHHS. The table below broadly sets out what will change:

 The top-line descriptors on invoices changed in September 2025,  while the actual numbers will change at the point of migration. The Standard Settlement Configuration (SSC) ID will become four digits (currently it is three), while the Line Loss Factor Configuration (LLFC) digits will change post-migration. These will then be updated on the Electricity Central Online Enquiry Service (ECOES). 

Please note that there may be a short period where the old descriptors remain on your contract. We will keep customers informed about this and any potential impacts as we approach the migration window.

Key changes to know:

1. Meter Timeswitch Code (MTC) will become Standard Settlement Configuration (SSC) regardless of migration status.

2. Line Loss Factor Configuration (LLFC) will be replaced by DUoS Tariff ID at the time of migration.

The new top-line will be in place from the industry go live date of 22 September 2025.

Every electricity supplier has an end date for migrating all customer meters to the new MHHS systems of 7 May 2027. To ensure this deadline is met, Ofgem introduced a modification called P487 in June 2026. If a supplier fails to migrate their customer meters on time, P487 restricts their ability to register any new customers and metering systems (MPANs) until the transfer is complete. However, they can continue supplying and billing their existing un-migrated customers.

At nBS, we qualified to start migrating our customer in the first wave, and migration is already well under way and set for completion by the May 2027 deadline.

P434 is an industry-wide modification which required all Non-Half-Hourly (NHH) Unmetered Supplies (UMS) to be Half-Hourly (HH) settled on a single primary Meter Point Administration Number (MPAN) by 30 September 2025. The aim was to migrate all NHH UMS MPANs by 1 October 2025 to enable UMS sites to be included in the MHHS migration, which will happen by May 2027.

If you have any NHH-UMS meters at your site and haven’t been contacted about the migration, it’s important to get in touch with your supplier immediately.