MHHS Rollout: The Practical Checklist for Multi-Meter Estates

If you own or look after a large estate, you’re probably used to small problems multiplying. One meter gets a wrong address. Another has a stale serial number. A third is on the “wrong” setup after a refurb. None of it feels urgent… until the bill lands and the numbers don’t add up.

Market-wide Half-Hourly Settlement (MHHS) turns that kind of drift into real cost and real time spent fixing it. Not because MHHS is “bad”, but because it makes your meter data and agent setup matter more often, in finer detail, and with less room for workarounds.

What MHHS is

MHHS is the move to settle electricity usage in half-hourly slices across the market, rather than relying on broader estimated patterns for many non-half-hourly supplies. Central systems went live in September 2025, and suppliers began migrating MPANs from 22 October 2025 in a phased rollout.

By February 2026, migration is underway. The programme’s “full transition complete” milestone is set for 7 May 2027, which is the end of the migration period.

What that means for you: some of your supplies may already be in MHHS arrangements, while others won’t move until later in the wave plan.

Why multi-meter estates feel MHHS more sharply

A single site with one meter can still have issues, but an estate brings extra complexity:

• More MPANs, more chances of mismatched details

• More tenants, switches, void periods and refurb projects that change how supply is used

• A wider mix of load types (workshops, cold stores, pumps, grain drying, holiday lets) that don’t behave like “average” consumption

Under MHHS, half-hourly data becomes central to how energy is settled. So when your meter technical details, appointments, or data flows are misaligned, it tends to show up as bill queries, delay, or repeated “corrections” rather than a one-off oddity.

Half-hourly readiness: which supplies should be treated as HH/AMR first

You don’t need to upgrade everything at once, but you do want to spot the supplies where better data pays back fastest.

As a starting point, focus on meters serving:

• Cold stores and refrigeration (steady load with spikes when defrost cycles hit)

• Grain drying (short, intense usage windows)

• Workshops and plant rooms (variable load that can hide peaks)

• Irrigation, pumping, aeration (seasonal patterns that estimates often miss)

The aim is practical: where half-hourly or frequent reads reduce estimation and make the bill easier to trust.

DC/DA alignment: your bills are only as clean as the data flow

One of the quickest ways estates get stuck is when the appointed agents don’t match what’s on record, or the “who does what” has changed over time.

Under MHHS, the detail and speed of validation matters, which puts more weight on getting these basics right:

• Is the right Data Collector (DC) and Data Aggregator (DA) appointed for each MPAN?

• Do you have a single approach across the estate, or a patchwork created by historic switches?

• Are meters being read on the expected schedule (especially AMR/HH)?

If you discover inconsistencies now, you can fix them before a migration wave exposes them in the middle of billing.

Pre-migration checklist: what to fix now

Think of this as “clean the labels before the scanner gets stricter”. Work through each MPAN and confirm:

1. Meter serial numbers match what’s on site

2. Site addresses are consistent and complete (especially where estates use names, units and outbuildings)

3. Profile class / meter configuration reflects how the supply is actually set up

4. Read frequency is correct and happening (and you can access the reads)

5. Recent site changes are reflected (new sub-meters, landlord supplies split, tenant changes)

If you only do one thing: build a simple estate meter register that ties MPAN, serial, address, and appointed agents together. It saves hours later.

Bill impact watchlist: what MHHS can reveal (good and bad)

More granular settlement can surface things you didn’t see clearly before:

• “Hidden” peaks that occur outside normal working hours

• Equipment cycling that looks small day-to-day but adds up across dozens of meters

• Proof that operational changes worked (a control tweak, a timer change, a plant upgrade)

It can be uncomfortable at first, but it also makes it easier to separate genuine usage from billing noise, if your data and agent setup are correct.

A practical next step for large estates

MHHS isn’t something sitting on the horizon. Migration is already happening, and estates with multiple meters are naturally more exposed to data and configuration issues.

You could work through each MPAN yourself: checking serial numbers, confirming site addresses, reviewing agent appointments, but across a large portfolio that quickly becomes time-consuming.

CLA Energy Services can help you review meter data quality and confirm that your appointed data agents are aligned across your estate. For multi-meter portfolios, that clarity helps prevent avoidable billing disruption as MHHS continues through to May 2027.

If you’d like support reviewing your estate’s readiness, speak to the CLA Energy Services team.