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.

Current time – industry testing is ongoing 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.

October 2025 – the migration window opens for suppliers and agents who have completed and qualified in their Systems Integration Testing (SIT). 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’ve chosen the ‘qualification’ route, whereby their systems and processes have been assessed to comply with new MHHS requirements. As above, when your business migrates will depend on when your energy supplier qualifies.

May 2027 – meter migrations are complete.

July 2027 – the new MHHS model will come 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're preparing to qualify 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. This could be either actual Half-Hourly (HH) data, data calculated between multiple readings, or in the case of Unmetered Supplies (UMS), data calculated from the settlement period

• 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

Qualification will occur in two windows for us:

Advanced Data and Metering Services are scheduled for the first migration window. currently scheduled to start in 2025.

The supplier qualification window will come later in the programme, and when we have more information, we'll be in touch with our customers.

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

If you haven't chosen any agents yet, we will appoint agents on your behalf, although they may not be your preferred choice. It's important to communicate your preferences so we can ensure the contracts meet both your needs 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 our 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 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 Non-Half Hourly (NHH) meters are configured.

If you have an Automated Meter Reading (AMR) or 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. However, we don’t currently believe this will involve a physical meter exchange.

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 they are kept up to date, and 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.

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:

Appoint a Smart Data Service (SDS) agent and a Metering Service (Smart) (MSS) agent.

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, we don’t currently believe this will involve 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 are currently scheduled for change in September 2025, with numbers changing at the point of migration. These will then be updated on the Electricity Central Online Enquiry Service (ECOES). As of September 2025, 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.

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:

Meter Timeswitch Code (MTC) will become SSC regardless of migration status.

LLFC will be replaced by DUoS Tariff ID at the time of migration.

Profile Classes will be discontinued post-migration, except for Classes 02 and 04, which will be used to identify Economy 7 and Economy 10 meters.

Here is an example of what to expect:

Market-wide Meter Reference Number Update - Current version

Market-wide Meter Reference Number Update - Post MHHS version

P434 is an industry-wide modification which requires 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 so that there are no more NHH UMS MPANs by 1 October 2025.

P434 will enable UMS sites to be included in the MHHS migration which will happen shortly afterwards.

We are in the process of migrating our Unmetered Supplies (UMS) customers from Non-Half Hourly (NHH) to be settled Half-Hourly (HH). If you are an npower Business Solutions (nBS) customer, we will be in touch with you throughout the migration process.

The key things to know are:

If you only have one primary Meter Point Administration Number (MPAN) assigned to your inventory, this will be the one converted to HH and your account number will not change.

If you have multiple MPANs across your inventory:

These will be moved to a single (primary) MPAN which will then be migrated to HH settlement.

If you have multiple inventories, for example across multiple sites, you may have multiple primary MPANs.

The account number related to your primary MPAN will not change.

Any MPANs no longer in use post migration will be terminated by your Distribution Network Operator (DNO).

If you have a seasonal meter:

After your primary NHH UMS MPAN has been migrated, your HH consumption will be calculated by a Meter Administrator (MA) on a single MPAN. This calculation will include all of your usage across your UMS inventory so your charges will reflect the usage all year round and take into account any seasonal load.

In all scenarios, there are no planned changes to bill cycles so this should remain as monthly, quarterly or annually. However, please be aware that your invoices may take longer to arrive as we will be completing additional validation checks to ensure they are accurate.

You will need to discuss this with your Unmetered Supplies System Operator (UMSO). Suppliers and UMSOs have been working together so that the UMSO can get in touch with you and make sure that the necessary changes to your inventory can be agreed.

If this has not happened, we would encourage you to contact your UMSO directly.