Picture a manufacturer with one large factory and a dozen smaller sites: a warehouse, a few offices, some depots. The factory has been settled on half hourly data for years. The smaller sites have been settled on standard profiles, which estimate when they use electricity rather than measuring it. Between now and May 2027, every one of those smaller meters moves across to the half hourly system.
That example is illustrative, but the change is real and nationwide. Elexon, which runs electricity settlement in Great Britain, describes Market wide Half Hourly Settlement (MHHS) as one of the biggest changes to the electricity retail market since competition began in the late 1990s.
Most of the work falls to suppliers. But it reaches into your metering contracts, your data and, over time, the tariffs on offer. Here is what you need to know.
Where the programme has got to
Settlement is how the market works out who used what, so that each supplier pays for the electricity its customers consumed. Until now, many smaller business meters have been settled on estimates. MHHS replaces those estimates with half hourly data for every meter in the country.
Suppliers started moving meters on 22 October 2025. By February 2026, more than two million meters had moved. By May, more than 8.4 million had moved out of roughly 33 million in total, and by early July more than 14 million, over 40%. Elexon expects around 80% of meters to have moved by October 2026.
The dates that matter
28 October 2026: every supplier must be able to accept meters under the new arrangements.
7 May 2027: the migration period ends.
2 July 2027: the settlement timetable shortens from 14 months to four.
The deadlines are enforced. A supplier that has not qualified by 28 October 2026 cannot register new Meter Point Administration Numbers (MPANs), the unique numbers that identify each supply, until it does. From the same date, meters can no longer be moved back to the old arrangements when you change supplier.
Your larger sites may already be there
Since 1 April 2017, meters in Profile Classes 5 to 8 have had to be settled half hourly where capable metering is installed. For many larger businesses, that covers the main sites, so the headline change may look small.
The difference is across the rest of the estate. Smaller sites such as shops, offices, depots and plant rooms are more likely to still be settled on profiles, and these are the meters moving now.
Three things worth a closer look
Your metering and data contracts
The supplier agent roles behind every meter are changing. New Smart Data Service and Advanced Data Service roles take over from the Data Collector (DC) roles, and the Data Aggregator (DA) roles are being removed altogether. The Meter Operator (MOP) role carries on in a similar form, as the Metering Service. The old arrangements run alongside the new ones while the last meters migrate and older settlement periods are reconciled. If you contract your own MOP or DC, it is worth checking how those agreements carry across before they next renew.
Data quality
Settlement currently takes 14 months to finalise. From July 2027 it will take four. That timetable governs how suppliers are settled rather than your invoice directly, but it means industry data will be locked down far sooner. A faulty meter, missing reads or wrong site details are better found now than later.
New ways to save
Elexon links half hourly settlement to a fivefold increase in consumer led flexibility, to around 12 gigawatts (GW) by 2030. Half hourly data also gives suppliers what they need to design tariffs that reflect when electricity is used. For sites with load that can move, such as refrigeration, heating, pumping or vehicle charging, the cost of when you use electricity will become more visible, and more open to management.
You do not need to manage the migration yourself. The value comes from paying attention while it happens.
Questions to ask your supplier
Three questions are reasonable to ask. Which of our MPANs have moved, and which are still to move? Will anything change on our bills or metering charges as a result? And if a site that has moved still shows estimated reads, why?
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Request a free reviewWhat this means for your business
For most businesses, MHHS will happen quietly in the background. Knowing how each site is metered and settled, catching estimates and errors early, and reviewing metering and data agreements before they renew all make the transition smoother. Over time, better data may also open up tariffs that reward shifting consumption away from peak periods.
Energy Planner is independent, not tied to any supplier, and arranges electricity contracts and metering services for businesses across Great Britain.
Sources: Elexon, Market wide Half Hourly Settlement, MHHS Programme, key milestones, MHHS Programme, migration, Elexon, suppliers start moving meters (22 October 2025), Elexon, more than two million meters (16 February 2026), Elexon, over a quarter of meters moved (14 May 2026), Elexon, 11.3 million migrations (17 June 2026), Elexon, MHHS Transitional Operations Group (10 July 2026), Elexon, P487, Elexon, P272 (Profile Classes 5 to 8), Elexon, SVA qualification and new data service roles. This article is general information as at October 2026, not advice on your specific circumstances. Outcomes depend on market conditions and your own contracts, so it is worth confirming the detail for your sites.