And why has the timeline been pushed back?
You might’ve heard the term Market-wide Half-Hourly Settlement (MHHS) mentioned a lot over the past few months, but what exactly is it, and where are things now?
In short, MHHS is a big change to how electricity is settled across the UK energy market. It will make sure that energy usage data is collected and settled using actual half-hourly readings, rather than estimates or longer intervals. That means more accurate billing, better demand forecasting, and a step forward in helping the grid respond more flexibly to consumer behaviour.
MHHS is led by Ofgem, and originally it was due to go live in stages from 2025 through to 2026, but at the end of 2024, that timeline changed.
What’s changing and why?
In November 2024, Ofgem approved a formal change request to shift the programme’s timelines by around 6.5 months. This was to give additional time for integration testing and to reduce the risk of a rushed or unstable rollout.
The new target dates include:
- Central systems ready – delayed from March 2025 to late September 2025
- Migration begins – now expected late October 2025
- Migration ends – pushed to May 2027
- Full transition to new settlement timetable) – now due July 2027
According to the MHHS programme team, this change was necessary due to delays in Systems Integration Testing (SIT), which is a critical stage in getting all parties’ systems to communicate effectively. High defect levels, lack of test readiness, and under-resourcing across some participants slowed things down more than anticipated.
Why is MHHS important?
This isn’t just a technical upgrade. MHHS will fundamentally change the way energy is managed in the UK. It enables:
✅ More accurate bills – based on actual usage, every half hour
✅ Greater flexibility – helping customers benefit from time-of-use tariffs
✅ Smarter grid management – with better forecasting and demand balancing
✅ Progress toward Net Zero – by supporting low-carbon tech like EVs and heat pumps
The delay is disappointing for some, but it also means more time to get it right. A well-managed rollout reduces the risk of billing errors and system failures once the switch happens.
What happens next?
The MHHS team is now working to the new delivery plan, with updated milestones being reviewed and published fortnightly. The programme is still progressing, just on a slightly slower track.
We’ll be keeping a close eye on all developments, and if you’re a client of ours, don’t worry. We’ll make sure you’re supported through every step of the MHHS rollout, including what it means for your contracts, billing, and data reporting.
Need help navigating industry changes like MHHS?
We’re here to simplify the energy side of your business — so get in touch for friendly, expert advice.
☎️ 01738 474630
✉️ theteam@herestheplan.co.uk
