What is Market-wide Half-Hourly Settlement (MHHS)?

Your MPAN / Supply Number is usually on your invoice and may appear like the image below (see the Distributor ID).

With the move to MHHS, Standard Settlement Configuration will replace Meter Time Switch Code, and Distribution Use of System (DUoS) Tariff ID will replace Line Loss Factor Class.

Profile classes 02 and 04 with traditional meters won’t change.

The profile class of all other non-half-hourly metered supplies will change to ‘00’ – this is the first two digits of the supply number on your bill.

Unmetered supplies and AMR Current Transformer (CT) meters will change profile class before migration to MHHS; followed by AMR Whole Current (WC), smart and single rate traditional meters.

These changes won't interrupt your supply or switch you to another supplier.

The roles of MOPs and DCs are evolving. MOPs will transition to Metering Services, and DCs will transition to Data Services. Existing MOPs and DCs will need to qualify for accreditation in these new roles. The specific details will depend on the agent you have a contract with and their post-MHHS roles. Please discuss their status with them.

If your appointed agent is a qualified MHHS service provider, we’ll re-appoint them and you won't need to do anything. 

If your service provider’s qualification is planned later than May 2026, we’ll work with you and them to align migration dates where possible.

If your agent isn't MHHS qualified by October 2026 or is exiting the market, we’ll appoint an approved agent on your behalf.

Energy suppliers will follow the updated industry Change of Agent process. We’ll work with you, as well as with metering and data service agents to make sure they’re appointed to the new roles correctly. Agents will still be responsible for managing metering equipment and collecting meter read and data information as they do now.

This process will affect existing and new customers. If you’re switching to us, we’ll carry out migration to MHHS during the registration process.

The impact of these changes will depend on your price plan and any new or additional costs we incur during this transition. We’re working through how MHHS impacts contracts and will let you know any changes to rates ahead of migration.

Due to the scale of this change and the new service processes and systems, we’re currently unable to predict these costs. We’re working diligently to finalise these. If we do need to add any additional costs, we’ll always inform you in writing beforehand.

Future costs across the energy industry will be lower with MHHS in place, than without this regulatory change. So, while costs may increase in the short term, they won’t rise as sharply, saving you money in the longer term. Ofgem predicts that GB consumers should see net benefits of £1.6bn-£4.5bn by 2045.

If a supply is unmetered, we’ll also need to appoint data and meter administration agents, so your bills will include additional fees.

We’ll use your half-hourly data primarily for forecasting and settlement purposes, to help us accurately predict energy demand and manage supply more efficiently. Additionally, we’ll use your half-hourly data to provide more accurate billing and to improve our product offering.

Our smart data guide and our privacy policy set out the standards you can expect from us when we request or hold your business’s information, including your half-hourly meter readings.

When your supply switches to half-hourly settlement, meter and data agents will be appointed to manage your energy data. These roles and agents might change again during the move to the new settlement system. They’ll be set up for you automatically unless you choose to appoint your own.

Please give us an up-to-date meter reading each month. This will help us make sure your account is billed accurately when your meter point migrates to the new arrangements.

If you’ve received an estimated bill, it’s important to send us an up-to-date meter reading so we can ensure you’re billed accurately ahead of migrating to MHHS.

To submit a meter reading, log in to Manage My Account or contact our customer service team.

If you’re on our variable business rates, you can switch to another supplier at any time (if any amount due is unpaid we may object to the switch). However, all suppliers will be moving non-half-hourly and unmetered supplies to half-hourly settlement. Another supplier may require your supply to be updated before they register it, or they may update it themselves after registration.

If you have an existing contract, you can’t switch to another supplier until the contract end date. Once your contract expires, you’ll be free to switch to another supplier.

You can check your terms and conditions here.

• By 22 October 2025: All unmetered supplies switch to half-hourly settlement under the current setup. This is part of an industry change called Modification P434, to prepare for MHHS.
• October 2025 – May 2027: Unmetered and other supplies move to the new MHHS system over 18 months. This may mean further updates, like changes to metering and data services.

No, you don’t need to have a meter installed. Your supply will continue in the same way.

Yes. When your supply moves to half-hourly settlement, multiple MPANs will be merged so there’s only one MPAN per inventory. Any extra MPANs will be removed, and their energy use will be combined with the remaining MPAN.

The primary supply number (MPAN) that will be retained will appear on your invoice.

No, all your unmetered supply equipment will remain connected. If you want to make changes to your equipment or its energisation status, please contact your UMSO.

You can find a list of UMSOs, their contact details and which MPANs they cover here.

This role is defined by the electricity industry to manage unmetered supplies, making sure the arrangements for unmetered supplies are correctly applied. Each electricity network operator appoints a UMSO who ensures the following:

• Establishing a connection agreement
• Maintaining an accurate inventory of unmetered equipment
• Creating and updating an Unmetered Supplies (UMS) Certificate.

A phased plan and early migration for unmetered supplies will allow plenty of time ahead of the MHHS transition for suppliers and Unmetered Supply Operators (UMSOs) to resolve any issues that may arise.

This is an industry-wide regulatory change that all unmetered supplies must undergo, mandated by Ofgem under P434. All energy suppliers are updating unmetered supplies to comply with this change by October 2025.

If you’re on our variable business rates, you can switch to another supplier at any time (if any amount due is unpaid we may object to the switch). However, all suppliers will be moving unmetered supplies to half-hourly settlement. Another supplier may require your supply to be updated before they register it, or they may update it themselves after registration.

If you have an existing contract, you can’t switch to another supplier until the contract end date. Once your contract expires, you’ll be free to switch to another supplier.

You can check your terms and conditions here.

Yes, your unmetered supplies will now be billed monthly.

Yes, we’ll create a new invoice structure number for you, but your billing details, like direct debits and electronic billing will stay the same. If you have multiple sites grouped on one bill, we’ll keep them grouped together in your new invoice structure.

If your existing contract ends before the change of measurement class is completed, you can get in touch with us to discuss your options. Otherwise, you’ll be temporarily placed on our VBR NHH Street lighting / Unmetered supplies tariff; then after the change, you’ll move to our VBR HH unrestricted LV and LVS tariff. You can find our VBR here.

The impact of these changes will depend on your tariff and whether you have multiple supply numbers (MPANs) within your unmetered equipment inventory (as agreed with your Unmetered Supply Operator (UMSO).

You’ll pay one standing charge per inventory instead of several.

You’ll move to our VBR HH unrestricted LV and LVS tariff. You can find more information about our current VBR on our out of contract rates webpage

Your existing rates will not be affected by the change of measurement class. We’ll incur higher costs when we move your supply to half-hourly settlement, but we won’t pass these on to you.

When your contract ends, the renewal offer will be based on half-hourly settlement.

Your invoice will include additional charges to cover the cost of your data collector and meter administrator. We’re appointing these agency services under the regulatory obligation to prepare for MHHS.

When your contract ends, the renewal offer will be based on half-hourly settlement.

All AMR metering in Britain will align to how half-hourly meters operate, to record and bill consumption every 30 minutes.

In most cases, no. Changes will happen automatically.

You may need a meter exchange if your meter can’t communicate electronically with the Meter Operator and Data Collector. We’re working with metering and data operators to identify affected meters. If your meter isn’t communicating, we’ll be in touch with you to arrange an appointment.

Under the new rules, your bill will be a total of the energy you used in every 30-minute interval during that billing period.

If you’d still prefer to get bills based on meter readings, your AMR meter will need to be exchanged to a smart meter, which you may be charged for.

All CT meters will move to half-hourly settlement and billing from March 2026, as part of P432.

We’ll be in touch with affected customers from February 2026. If your CT meter isn’t collecting half hourly data, it may be exchanged. You won't be charged for this.

P432 is a regulatory requirement that ensures all CT connected advanced meters currently settled non-half-hourly are updated to half-hourly settlement by suppliers. It’s mandatory, introduced by Elexon and approved by Ofgem as an early step of the MHHS rollout.

If you’re on an SSE Protect or SSE Choice plan, your pricing will remain as set out in your contract.

If you’re on a flexible plan, half-hourly pricing and billing will now apply to your CT supply.

If you have a CT meter and are on our variable business rates (VBR), your tariff will be updated to VBR Business HH (Measurement Class (MC) C&E). Please see our current VBR pricing details.

Whilst we aim not to change your IST, there may be circumstances that mean we need to do so. If changes are made, you’ll be able to see them on your next invoice, and billing will run concurrently between ISTs.

MIC is the maximum electrical capacity (in kVA or MW) the Distribution Network Operator (DNO) makes available to your site at any time. It's also known as 'available capacity'. All half-hourly customers must have an agreed MIC. If you exceed it, available capacity charges apply, which can be much higher than standard rates.

If your CT meter is currently non-half-hourly, to give you time to understand your usage, you won’t be charged for available capacity for the first 12 months following the update to half-hourly. We recommend reaching out to your DNO to confirm your MIC within 12 months. If you don’t contact them, they’ll calculate this based on the highest peak recorded during that time.

Unsure which DNO covers your supply? You can find a list here.