Ofgem is introducing Market-Wide Half-Hourly Settlement (MHHS) – a major reform of the UK electricity market that will change how all energy use is measured and billed.

Today, only large commercial sites are settled using half-hourly data. Everyone else is billed using profiles or estimates based on average usage. MHHS will change that.

From 2025, every meter – residential or commercial – will be settled using real half-hourly data.

This shift is designed to make the energy market more accurate, flexible and efficient. It means bills will reflect real energy use, suppliers can create smarter tariffs, and the whole system will be better equipped to support renewables and demand flexibility.

Why MHHS is being introduced

MHHS supports a smarter, lower-carbon energy system and brings benefits across the board:

More accurate billing and reduced financial risk

Settling energy use half-hourly, removes the uncertainty caused by estimated profiles. That means fewer billing discrepancies and better alignment between what’s bought and what’s used.

Enabling flexible, innovative tariffs

With real-time data, suppliers can offer time-of-use tariffs, demand flexibility, and options like EV charging incentives or battery storage.

Supporting net zero

More granular data helps balance supply and demand, integrate renewables, and reduce costly peaks – all contributing to a lower-carbon grid.

Faster settlement timelines

Settlement processes will shorten from around 14 months to about 4, improving efficiency and reducing risk.

Ofgem expects MHHS to deliver £1.6 to £4.5 billion in net benefits to consumers between 2021 and 2045.

How MHHS will work

A few key changes will shape the new system:

• New roles and responsibilities
  

  Existing market roles will evolve. For example, Meter Operators and Data Collectors will transition into new services like Metering Service, Data Service, and the Market-Wide Data Service. A new role – the Meter Data Retriever (MDR) – will collect half-hourly data from smart meters for settlement.

• Centralised data systems

  A Market-Wide Data Service will handle aggregation, while a Load Shaping Service and Volume Allocation Service will estimate and allocate data for settlement.

  These systems will process huge volumes – eventually handling around 500 billion half-hourly readings each year.

• Migration of all MPANs
  

  Every meter point (MPAN) will move to the new system during an 18-month migration window starting late 2025.

• Data consent and privacy
  

  Consumer consent and data access will be managed carefully under the Retail Energy Code, ensuring privacy is protected.

Implementation timeline

We’re helping clients prepare for MHHS ahead of migration starting in late 2025.

If you’d like to understand how this could affect your sites or metering setup, our team is here to help.