Market-wide half-hourly settlement (MHHS) means suppliers will be charged for the electricity their customers actually use in each half hour, instead of an estimate based on standard usage profiles. The move began in October 2025 and is due to finish in May 2027. If you have a smart or advanced meter, your half-hourly readings become part of how your electricity is settled, so it's worth asking your supplier for them.
What it is
Large sites have been settled half-hourly for years. Most smaller sites have been settled using standard profiles, which are estimates of when a typical customer uses electricity. MHHS replaces those estimates with actual half-hourly readings wherever a meter can provide them.1
The programme's stated objective is "to maximise the opportunities provided by smart metering by developing and implementing an enduring process for MHHS, that delivers benefits for consumers and enables a smart, flexible energy system."2
Who runs it
Ofgem decided to go ahead with MHHS on 20 April 2021.1 Ofgem is the programme sponsor and appointed Elexon as Senior Responsible Owner and Implementation Manager. Delivery is led by the energy industry.2
The timetable
| Date | Milestone |
|---|---|
| 20 April 2021 | Ofgem decision to introduce MHHS (originally planned to finish in October 2025) |
| 21 October 2025 | Migration to the new arrangements began, for all meter types |
| 7 May 2027 | Migration due to be complete, with all energy settled under the new arrangements |
| 2 July 2027 | Settlement moves from a 14-month to a four-month timetable |
Dates as published by Ofgem and the MHHS programme in November 2026. Check the programme's milestone page for the latest.1, 3
What it means for your organisation
- You don't need to do anything to be moved across. Your supplier handles it.
- Microbusinesses can't opt out. Ofgem's decision says half-hourly data will be processed for settlement for domestic customers unless they opt out, and that microbusiness customers will not be able to opt out.1
- Tariffs may change. Ofgem expects MHHS to encourage suppliers to offer tariffs that reward using electricity at cheaper times of day, known as time-of-use tariffs.1
- Half-hourly data becomes standard. If your meter records half-hourly readings, your supplier uses them. Ask for a copy and you can see exactly when your sites use electricity.
Under half-hourly settlement and time-of-use tariffs, the time of day you use electricity will matter more. Understanding your half-hourly pattern now, including what runs overnight and at weekends, will help you choose a suitable tariff and reduce costs.
Sources
Questions people ask
When does market-wide half-hourly settlement finish?
Migration is due to be complete on 7 May 2027, with the move to a four-month settlement timetable on 2 July 2027, according to the MHHS programme's published milestones.
Do I need to do anything?
No. Your supplier moves your meters across. It is worth asking them for your half-hourly data, so you can see when your sites use electricity.
Can a business opt out of half-hourly data collection?
Ofgem's 2021 decision says microbusiness customers will not be able to opt out of their half-hourly data being processed for settlement. Domestic customers can opt out.
