Market-wide Half-Hourly Settlement (MHHS) is moving electricity supply points in Great Britain to half-hourly settlement, using actual consumption where available and estimates where it is not. It covers England, Scotland and Wales, rather than Northern Ireland. For energy brokers, Milestone 14 on 28 October 2026 is the next supplier-readiness deadline [1]. The opportunity is better consumption evidence for procurement and validation, where the data is available and you have authorised access to it.
Migration is underway and continues to May 2027. Check each client's position with its supplier rather than assuming the whole portfolio moves on one date. Settlement changes do not automatically change the client's agreed retail tariff.
This guide covers what MHHS changes, the remaining milestones, and how brokers can prepare their data and bill-validation processes during the transition.
What is Market-wide Half Hourly Settlement?
MHHS changes the electricity market's settlement process. Large sites and some smaller sites already use half-hourly settlement. Many other sites have been settled using meter readings combined with standard profiles that estimate when consumption occurred. A customer's retail bill and the supplier's settlement calculation are related, but they are not the same calculation.
Under MHHS, actual half-hourly data is used where available. Missing readings and sites without usable half-hourly data still require estimation or load shaping [3]. A smart meter does not guarantee that every interval is actual. Keep the measured, estimated and substituted status with the data so you know what each figure represents.
More granular settlement strengthens suppliers' incentives to offer tariffs and services that reward flexibility. It can support shape-based procurement and load-shifting advice, but it does not require every client to move to a time-of-use tariff or guarantee a lower bill. The commercial effect depends on the client's contract, usage and available offers.
What changes at Milestone 14 on 28 October 2026?
By Milestone 14 on 28 October 2026, suppliers must be MHHS Qualified and Service Active, able to accept MPANs under the new arrangements. Reverse migration to non-half-hourly settlement on a supplier switch then ceases [1]. This is a supplier-readiness milestone, not the date every customer finishes migration.
Milestone 15 on 7 May 2027 is the migration-completion target, assessed against the programme's acceptable end states. Milestone 16 on 2 July 2027 is the planned cutover to the shorter settlement timetable [1]. Check a site's migration status separately from these market-wide dates.
Three practical changes land on your desk during that window.
Profile classes stop being the reference point. The profile class you've used to categorise a site, and the assumptions built on top of it, are being phased out in favour of new settlement arrangements. Any internal register, quoting template, or client report keyed to profile class needs a plan.
Quotes can become more shape-sensitive. Half-hourly history helps compare offers against the way a site uses energy. Whether charges vary by time of day depends on the contract; a flat-rate agreement does not become a time-of-use tariff just because the site migrates.
Data volume per client can rise sharply. A complete half-hourly series contains 17,520 periods in a 365-day year, or roughly 1.4 million across 80 meters. These are periods to manage, not a guarantee of that many actual readings.
How does MHHS change bill validation?
Invoice validation still starts with the contract. Reconcile consumption, rates, standing charges and any pass-through components to the billing period. Where time-of-use rates or interval-based charges apply, validate the relevant periods and bands rather than relying only on the monthly total.
A time-band error, incorrect multiplier or substituted reading can hide inside an otherwise plausible total. Interval-level checks can expose those problems, although not every bill or charge needs a different rate for every half hour.
The useful change is the evidence available to support a query. With the relevant interval series, data-quality status and agreed charging rules, you can explain which volumes or charges do not reconcile and ask the supplier for a breakdown.
A 30-day period contains 1,440 half-hourly intervals per meter. Managing those records, rate versions and exceptions across a portfolio calls for a controlled process, whether the starting point is a spreadsheet or a dedicated platform.
What should brokers put in place during the transition?
Five practical steps help turn better data into a repeatable client service.
- Audit your client register against migration status. Know which sites have already moved, which are scheduled, and which still sit on a profile class. You cannot advise on a shape you haven't seen.
- Arrange authorised access to useful consumption history. Confirm the supplier or data-service route, permissions, coverage and quality flags. A longer history makes renewal comparisons more representative, but MHHS does not automatically deliver that history to a broker.
- Match validation to the contract. Reconcile interval-based charges period by period where applicable, while also checking fixed charges, billing dates, metered totals and the basis of any pass-through item.
- Brief clients before migration or renewal. Explain what changes in settlement, which data you can obtain and whether their own tariff or billing arrangements will change.
- Define the advisory service. Load-shifting analysis and shape-based procurement can become more useful where interval evidence, suitable tariffs and client flexibility are available. Scope the work and its assumptions before promising savings.
The operational challenge is keeping data, contracts and exceptions connected. A repeatable review process helps brokers build an advisory service without repeatedly reconstructing each site's evidence.
How Utilified approaches half-hourly data at scale
UMS brings client accounts, sites, meter records, invoices, tariffs and agreements together for utility operations and advisory work alongside your CRM. It supports interval and accumulation records, supported data intake, contract and tariff comparisons, and exception review. Feed coverage and validation depth depend on the supplier, market, configured rules and available source data.
For client delivery, the Custom Portal add-on provides configured branded views, with reporting governed by account access and setup. Joule is a separate add-on for assisted questions and workflows where enabled. For a British portfolio, confirm the data route, tariff configuration and client views required for the service before promising a particular level of half-hourly visibility.
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Frequently asked questions
What is Market-wide Half-Hourly Settlement?
MHHS changes electricity settlement in Great Britain to half-hourly periods. It uses actual consumption where available and estimates where it is not; it does not automatically change a customer's retail tariff.
When does MHHS take effect?
Migration is underway. The remaining targets are supplier readiness on 28 October 2026, migration completion on 7 May 2027 and the shorter settlement timetable on 2 July 2027. Individual sites migrate during the programme rather than all on one day.
How does MHHS affect energy brokers?
Better interval evidence can support procurement and validation, where brokers have authorised access. The practical work is checking data quality, migration status and contract terms, then matching the analysis to each client's service.
Do clients need a smart meter to be settled half-hourly?
No. Settlement can use estimated or shaped data where usable half-hourly readings are unavailable. Even a smart-metered series can contain estimates, so check its data-quality status.
How much data does half-hourly settlement produce?
A complete 365-day series has 17,520 settlement periods per meter. Local-clock days can contain 46 or 50 periods at daylight-saving changes; leap years have more periods. Keep timestamps and time-zone conventions consistent.
Related reading:
- What is invoice validation in energy management?
- What is a white-label energy portal?
- Utility management software vs spreadsheets: why growing portfolios need a platform
- Multi-site energy portfolio management: cutting through complexity
- The hidden cost of utility data complexity — and how consultants turn it into value
References
[2] MHHS Programme: Migration Sprints. Migration runs from October 2025 to May 2027.