Skip to main content

Introducing Market-Wide Half-Hourly Settlement (MHHS)

The energy industry is changing – and we’re getting ready to take a big step forward.

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

Market-Wide Half-Hourly Settlement (MHHS) is a major industry reform led by Ofgem to modernise the way electricity usage is measured and settled across Great Britain. It means that – instead of relying on estimated or infrequent meter readings – the energy system will increasingly use actual half-hourly data from smart and advanced meters to settle electricity usage more accurately and efficiently.

What this means for our customers

Brook Green Supply predominantly supplies half-hourly metering, so the programme won’t have a significant impact on many of our customers. That said, there will be changes that everyone should be aware of. For those not benefitting from half-hourly metering, the shift will unlock a more accurate and fairer energy experience – offering greater flexibility, more precise billing, and a system that better reflects how and when you use electricity.

Brook Green Supply's commitment to a smooth transition


We are fully engaged in this industry-wide reform and are working closely with our partners to deliver a seamless migration for our customers.

Technical & Metering

Not necessarily. We predominantly supply half-hourly metering. If your meter already records half-hourly data, it’s likely compliant. If not, we’ll work with you to upgrade to a Half-Hourly (HH) compliant meter ahead of your migration date. You’ll be contacted in advance if a meter change is required.
  • Smart meters are typically used in domestic or small business settings, often with two-way communication. Brook Green Supply does not currently support smart metering. If you have a smart meter installed, we will work with you to arrange the installation of a more suitable metering solution for your supply.
  • AMR meters are common in commercial premises and send readings from the meter to supplier automatically, usually one-way.
  • HH-compliant meters (for MHHS) must be able to record and send accurate readings every 30 minutes. If you already have a smart meter or an Automated Meter Reading (AMR) meter, it may already meet these requirements.
MHHS is a regulated industry requirement. If your meter is not capable of meeting settlement requirements, we face an obligation from Ofgem to upgrade it. Refusal may impact our ability to serve your account under the new framework and would be deemed a breach of contract.
In many cases, no action will be required from you – your existing meter communications should be sufficient for half-hourly data transmission. However, in some situations, upgrades or changes to the communications setup may be needed. We can work with you to support these changes.
Most AMR meters are compatible. However, we will assess compliance on a case-by-case basis. If your AMR meter does not meet the MHHS requirements, we’ll discuss your upgrade options with you.
No – the core structure of the Meter Point Administration Number (MPAN) will remain the same. However, under the Market-Wide Half-Hourly Settlement reform, some existing fields – such as the Profile Class – will be repurposed to support legacy metering and load-shaping functions. These changes are being introduced through the Retail Energy Code (REC) and will not affect how your MPAN is displayed or used in your billing or account management. You do not need to take any action – Brook Green Supply and the wider industry will handle these updates behind the scenes.

Billing & Contracts

If you already have half-hourly metering, you’re unlikely to notice a difference in how your bill is calculated. For customers who don’t yet have this type of metering, MHHS will gradually introduce billing based on actual half-hourly energy use.

Over time, MHHS is expected to encourage more flexible pricing options. This could create opportunities to reduce costs by shifting usage to lower-cost periods – but any changes to your pricing would only happen at contract renewal or by agreement.

Your billing method and frequency will remain the same. Invoices will be calculated using consumption recorded on a half-hourly basis to more accurately reflect your usage, rather than the traditional monthly reading.
Yes. All existing customer contracts remain valid.

If you're already on a half-hourly or flexible contract, you likely already benefit from time-of-use pricing – where the cost of electricity depends on when you use it. MHHS won’t change your current contract, but it will make these types of tariffs more widely available. This means more customers will be able to choose fairer, usage-based pricing options instead of being billed on estimates.

For Brook Green Supply customers, this means we’ll continue offering bespoke and flexible pricing options – and MHHS gives us even more accurate data to support those offers. There's no obligation to switch to a ToU contract unless it suits your usage and business needs.

Timing & Readiness

Migration begins in 2026 and will continue through to late 2027. We'll notify you well in advance of your planned migration window. Brook Green Supply will ensure a smooth transition, with no disruption to your energy service.

Yes – if you switch to a supplier that isn't yet qualified under the Market-Wide Half-hourly Settlement arrangements, your metering points will need to be moved back to legacy settlement process. This is known as reverse migration.

You won't need to take any action – the process is handled automatically between suppliers and industry systems. Your energy supply will continue as normal, and we’ll ensure smooth transition without disruption. If reverse migration applies to your switch, we’ll keep you informed.

No – delays are not permitted . Migration dates are set by Ofgem and can’t be delayed for individual customers. All suppliers must meet specific thresholds, which are minimum percentages of MPANs that must be migrated by certain deadlines.

These thresholds ensure the rollout happens smoothly and on time across the whole market. While you can’t defer your migration, Brook Green Supply will support you throughout the process with advance communication, site-level planning, and technical guidance to make the transition as straightforward as possible.

Customer Choice & Participation

No, MHHS is a regulatory requirement for all electricity suppliers and customers. It is designed to modernise settlement and improve efficiency and accuracy across the energy system.
Yes. You can access your consumption data through our market-leading Portal, which allows you to monitor meter readings, access invoices, and compare usage across multiple sites – all in one place.
Yes. Switching remains unaffected. If you switch supplier during your MHHS transition period, your new supplier will assume responsibility for your migration.

Privacy & Data Handling

Your half-hourly consumption data is managed under strict privacy controls that are set forth in the Retail Energy Code (REC), specifically through Schedule 12 (Data Access). This schedule outlines who can access your data, for what purposes, and the governance around access permissions.

It ensures that your data is handled securely and only used for valid settlement and service reasons. You also retain full rights to access, restrict, or review how your data is used.

No, if you've already provided consent via your existing contract or LOA, no further action is needed. You will be notified if any additional consents are required.
Only authorised parties within the electricity market (such as your supplier and data service providers) will have access – and only for legitimate settlement or billing purposes.

Insights hub

See more

Energy news straight to your inbox