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.

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 (MSS/MSA or 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.

Each supplier may have their own unique approach to this situation. Rest assured, if we are your chosen supplier, we will reach out to you as soon as more information becomes available.

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).

The top-line will be amended as follows:

• ‘Standard Settlement Configuration (SSC) ID’ will replace ‘Meter Timeswitch code (MTC)’
• ‘DUoS Tariff ID’ instead of ‘Line Loss Factor configuration (LLFC)’

The new top-line information will be reflected on the first invoice after the migration completion. However, there may be a brief period where contracts still mention the old industry descriptors. We will keep our customers informed about this and any potential impacts as we approach the migration window.

After the MHHS migration is complete, Profile Classes will no longer be used and will default to 00, except for Profile Classes 02 and 04, which will continue to be used to identify Economy 7 and 10 meters.

Market-wide Meter Reference Number Update - Current version

Market-wide Meter Reference Number Update - Post MHHS version

All meters have a MOP and DC appointed today and are usually charged directly or through the standing charge, depending on your contract and supplier.

In the future, more meters may have their metering charges applied directly, but it is not yet clear if this will result in the same, higher, or lower costs. Rest assured; we will communicate with our customers closer to their migration to explain the potential impacts of this transition.

This is similar to how the UK energy industry works today. If demand is completely unpredictable then you may not be able to take advantage of certain time-of-use products.

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:

Like suppliers, metering service providers will also need to adapt and qualify to become accredited in the new roles.

If you are uncertain about who supplies your current metering service, please contact your supplier.

Both the import and export suppliers will be responsible as they are registered to each respective Meter Point Administration Number (MPAN). Both suppliers will also need to ensure the meter has the same Metering Service (Advanced) (MSA) agent and Advanced Data Service (ADS) agent appointed. For more information, you will need to contact each supplier for further information.

If you’re our customer and currently have a Non-Half Hourly (NHH) meter or if your Half-Hourly (HH) meter is outside of signal range, your data and usage will continue to be read monthly or quarterly by agents working on our behalf.

MHHS will not change how existing NHH meters are configured. These will continue to be done over the air or by a physical site visit by a MSA agent using appropriate software for the meter, via instruction from both the import and export supplier(s).

The specific details will be determined by the agent you have a contract with and their post-MHHS roles. We will be in touch with our metering customers to talk through any changes to contracts ahead of time to make sure everything is a clear as possible.

The timing of your metering and supply renewal is not directly tied to MHHS. It will depend on when your contract is up for renewal and the specific Terms and Conditions (T&Cs) associated with it.

The commercial impact of MHHS is being assessed. However, 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.

P434 is an industry-wide modification which requires all Non-Half-Hourly (NHH) Unmetered (UMS) Supplies to be Half-Hourly (HH) settled on a single primary MPAN (Meter Point Administration Number) 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 Market-wide Half-Hourly Settlement (MHHS) migration which will happen shortly after.

We are in the process of migrating our UMS customers from Non-Half Hourly (NHH) to be settled Half-Hourly (HH). If you are an 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 DNO (Distribution Network Operator)

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.