How to Check Whether an SME Site Has Migrated to MHHS Before You Quote a Renewal

Migration to Market-wide Half-Hourly Settlement has stopped being a programme update and started showing up in quotes. As of 28 August 2026, 20.2 million meters had been migrated, roughly 60% of everything in scope, according to the Association of Meter Operators' summary of the programme's figures. Elexon's planning assumption is that around 80% will have moved by October 2026, as set out when it spoke on the next steps for MHHS in February 2026.

Brokers are left in an awkward middle period. Two identical-looking shops on the same street can sit in different settlement regimes: the migrated one has real half-hourly data behind it, while the other is still settled off an estimated profile. The practical question is how you tell, site by site, before you put a price in front of a client.

Checking a single MPAN

Start with the industry record rather than the supplier's customer service desk. The Electricity Enquiry Service (ECOES/EES) carries an MHHS indicator against each MPAN, shown as an icon and status in the supplier panel, and the same new data items are returned through the API. The REC's third-party user guide explains the marker and flags a trap worth knowing: for migrated MPANs, some legacy fields are still returned but no longer populated, and displayed consumption figures can go stale. If your quoting process scrapes ECOES for an annual quantity, check when that figure was last refreshed.

Other signals are reliable:

• Agent roles. The Meter Operator becomes the Metering Service, and the Data Collector and Data Aggregator roles are replaced by a Smart Data Service (smart and traditional meters), an Advanced Data Service (advanced and AMR meters) and central services performing aggregation. If the record still shows an MOP, DC and DA in the old shape, the point has not moved.
• Market segment. Migrated MPANs sit in a market segment: smart, advanced, unmetered or traditional. That segment, not the old profile class, now tells you who collects the data and how often.
• Data items on the bill and in flows. The Meter Timeswitch Code is superseded by the Standard Settlement Configuration, and Line Loss Factor Class references change as part of migration. Suppliers such as npower Business Solutions have published customer-facing notes confirming these descriptor changes and warning that contract documents may lag the industry record by a short period.

When you write to the supplier or the Metering Service, avoid the vague "has this site moved to MHHS". Ask instead for:

• the migration date for the MPAN;
• the appointed Data Service and Metering Service with effect from that date;
• whether half-hourly data is available from the migration date onward, and in what format.

Asking for a date and an agent name gets you an answer you can act on.

What actually changes at the meter point

Migration is a settlement change, not usually a physical one. Most sites keep the same meter and the same tariff structure. The difference is that actual half-hourly volumes flow into settlement instead of an estimated profile shaped by class and standing data. Elexon expects to process up to 500 billion half-hourly readings a year once implementation completes, as noted in its update on supplier migration progress.

One change has direct commercial consequences. From Milestone 14 on 28 October 2026, an MPAN cannot be moved back into the non-half-hourly regime on a change of supplier, per the MHHS Programme's milestone documentation. Migration is a one-way door, so any pricing assumption that a switch resets a site to NHH treatment is wrong from that date.

Pricing renewals either side of the line

For a pre-migration site, the supplier prices shape risk from a profile class average plus whatever it knows about the sector. Reconciliation follows the old settlement runs, and the true-up can move against a client whose actual consumption pattern differs from the profile: a bakery loading heavily before 7am, say, or an industrial unit running a second shift. Expect that risk to stay priced into the unit rate as a shape or profile allowance.

Where a site has migrated, the supplier settling it has genuine half-hourly volumes. That usually means a tighter shape assumption and a better chance of the incumbent pricing a retention offer the market cannot beat on estimates alone. The counter is competitive: an alternative supplier quoting the same site is still working from whatever data you can obtain and pass on. Before you go to market, get the half-hourly data out of the current arrangement and into your own file, because after a switch the appointed Data Service may change and the historic series does not automatically follow the customer in a usable form. A letter of authority that explicitly covers half-hourly data from the Data Service, not only the supplier, saves a fortnight.

There is a timing point for contracts starting in the next few months. If a site is due to migrate during the term, part of the period will be settled on estimates and part on actuals. Ask the supplier how the shape allowance is set and whether it is reviewed after migration. Some will confirm in writing that rates are not re-opened; some will not.

The sites most likely to be left until last

Stragglers cluster in predictable places: unmetered supplies and street furniture; sites with dumb or non-communicating meters and no smart replacement booked; related MPANs at multi-meter premises where one point blocks the set; meter points with disputed or incorrect standing data; and customers sitting with small suppliers or on deemed and out-of-contract terms where nobody has pushed the exchange through. Ofgem's approval of Elexon's P487 modification tightens the incentive on suppliers to clear exactly these tails ahead of the Milestone 15 deadline of 7 May 2027, which is why brokers are now fielding more meter exchange calls on small sites.

Dates that matter from here

• 28 October 2026 (Milestone 14): all participants qualified and service active; MPANs can no longer return to NHH on change of supplier. Around 80% of meters expected migrated by this point.
• November 2026 to spring 2027: the migration tail, dominated by hard cases and small supplier portfolios, with P487 pressure on suppliers.
• 7 May 2027 (Milestone 15): end of the 18-month supplier migration window; every MPAN should be in the new arrangements.
• July 2027: the programme plan has full settlement under the new arrangements operating, after which legacy settlement systems are retired once the final reconciliation of old-regime settlement dates completes.

A checklist to run at every renewal

Before you quote, and while the client is on the phone:

• Check the MHHS indicator and migration date for each MPAN on ECOES, and note the market segment and the appointed Data Service and Metering Service.
• Treat any consumption figure shown against a migrated MPAN as potentially stale; source volumes from the half-hourly data instead.
• Request 12 months of half-hourly data now if the site has migrated, and store it yourself rather than relying on post-switch access.
• For an unmigrated site, ask the supplier for the scheduled migration window and confirm in writing how the shape allowance behaves if migration falls inside the new term.
• Flag sites with dumb meters, unmetered supplies or multiple related MPANs as likely stragglers, and get the exchange booked before the contract start date.
• Reconcile the MTC-to-SSC and LLFC changes against the client's bill so a descriptor change is not mistaken for a pricing error.

Keep a migration status column in your portfolio tracker and update it monthly. Over the next eight months it will explain more quote variances than any other single field.