MHHS Meter Migration- British Gas

Hello

From 4 September 2026, we'll begin migrating our electricity customers to half-hourly settlement as part of the Market-Wide Half-Hourly Settlement (MHHS) programme.

MHHS is an industry-wide change that requires all electricity consumption to be settled using half-hourly data. All UK energy suppliers must be MHHS compliant and have completed MHHS migration before May 2027. 

As part of this change, our BG Lite customers with advanced (AMR) meters will move to half-hourly billing. This will happen in phases, not all at once. 

What's changing 

Our mutual BG Lite customers with advanced (AMR) meters will start to see changes to their billing from 4 September 2026. 

Once these customers have migrated to MHHS:

• Their electricity usage will be settled every 30 minutes.

• Their bills will be based on half-hourly consumption data.

• They'll no longer need to send us meter readings.

• Actual consumption data will be displayed on their bills instead of estimated consumption and meter readings (see example attached).

This is a change to how electricity consumption is recorded and presented on bills - it isn't a change in supply or contract terms.  

How we'll support affected customers

We'll contact BG Lite customers with advanced (AMR) meters whose billing is changing as a result of MHHS migration to let them know what to expect.

Customers who are already billed half-hourly won't receive communications as they won't see any changes.

Customers with smart and traditional meters will continue to submit meter readings and won't see any changes to their bills.

What this means for you

If you support customers with bill validation or consumption analysis, you may notice some differences after they go through MHHS migration:

• Invoice formats and line items may look different.

• Consumption data may be presented differently to non-half-hourly bills (see attached an example of NNH versus HH billing).

• Validation tools may need to support half-hourly data.
• Historic comparisons may require additional consideration because data is being recorded differently.

If you use third-party validation software, please check it can process half-hourly data.

System differences to be aware of

We currently operate with two account management systems that will be affected in different ways by MHHS migration.

BG Lite (Ignition)

• We'll start migrating BG Lite customers first, actively moving them to half-hourly billing from 4 September 2026.

BGB (Salesforce)

• BGB customers won't see any changes until after 5 October 2026. From this date, they may be moved to half-hourly billing at their point of renewal.

Broker Portals

• There will be small changes to how you quote using both our BGB (Salesforce) broker portal and BG Lite broker portal as a result of MHHS transition. We'll be in touch separately to ensure you're fully prepared ahead of these changes.

What you need to do

To be ready for our MHHS migration starting on 4 September 2026, please ensure that you:

• Review your invoice validation processes and tools.

• Check any third-party validation solutions can process half-hourly data.

• Familiarise yourself with half-hourly billing and invoice formats.

• Share this update with colleagues who support customer billing enquiries.

• Review our half-hourly metering information - click here to visit the half-hourly billing section on our webpage.

We're here to help

We'll support you through this change with:

• A dedicated MHHS webpage containing latest updates, guidance and FAQs - visit our MHHS webpage here

• A comprehensive broker FAQ document (see attached)

• Help and support when you need it - please reach out to your Business Development Manager (BDM).

Thanks,

Your British Gas Team