MHHS - glossary 

Jargon busting: understanding Market-wide Half-Hourly Settlement (MHHS)

Like many energy-industry initiatives, Market-wide Half-Hourly Settlement – or MHHS for short – is full of technical terms and acronyms. Use our guide to discern your ADS from your SSC so you can make more sense of this important industry development.

Advanced Data Service (ADS)

A new MHHS role responsible for collecting and processing electricity consumption data from advanced electricity meters, which include Half-Hourly (HH) and Automated Meter Reading (AMR) meters. The ADS replaces the pre-MHHS Data Collector (DC) role and ensures that consumer data is ready for central settlement.

 

Advanced Market Segment

Consumers with advanced meters – so existing Half-Hourly (HH) meters and also any Automated Meter Reading (AMR) meters – sit within the Advanced Market Segment. Within this area, meter data is handled by the Advanced Data Service (ADS), and meter maintenance is managed by the Metering Service Advanced (MSA).

 

Advanced meters

Advanced meters automatically record electricity use in half-hourly periods (or more frequent time periods) and allow suppliers to access this data remotely.

 

Advanced Retrieval and Processing Service (ARP)

The ARP collects and prepares half-hourly electricity consumption data from advanced meters, making sure this data is ready for use in the settlement process.

 

Agent appointments

The process of assigning specialist agents to manage metering and data services, which are required to fulfil MHHS roles.

 

Annual Consumption (AC)

Under MHHS, Annual Consumption replaces Estimated Annual Consumption (EAC). It reflects the expected yearly electricity consumption for a meter supply point, using more accurate data sources.

 

Automated Meter Reading (AMR) meter

A type of meter that automatically sends electricity consumption data to the supplier without needing a manual reading. AMR meters are part of the Advanced Market Segment under MHHS.

 

Central Switching Service (CSS)

The national system that manages all electricity and gas supplier switches. It handles switch requests, deals with objections, and updates the registration systems once a switch is complete.

 

Central systems

The national infrastructure that manages key processes across the energy market — including supplier switching, meter data handling, registration updates and settlement. These systems are operated by different central bodies (like Elexon or the Data and Communications Company) and ensure the whole market runs smoothly and consistently.

 

Change of Agent (CoA)

A business process where a supplier updates one of the companies it has appointed to carry out key services — such as metering or data collection. Under MHHS, this process must follow new rules to make sure data flows stay accurate during the switch.

 

Change of Supplier (CoS)

A process where a customer switches from one electricity supplier to another. Under MHHS, this process is supported by more accurate and timely data, helping to reduce delays, improve switching visibility and ensure smooth handovers between suppliers.

 

Clean Power 2030

The UK government’s target to fully decarbonise the electricity system by 2030. MHHS supports this goal by enabling more accurate and responsive energy data, helping the market to adopt flexible tariffs, low-carbon technologies and customer-led energy use.

 

Connection Type

Specifies the physical type of electricity connection at a site and helps determine which meter types can be installed. Connection codes include: W – Whole Current (used with smart/traditional meters), L – Low Voltage Current Transformer (LV CT), H – High Voltage Current Transformer (HV CT), E – Extra High Voltage Current Transformer (EHV CT), U – Unmetered. Smart meters can only be used on W connections, while advanced metering supports W, L, H, and E — but not U.

 

Consumption profiles

These estimate how electricity is typically used by a specific type of consumer over time and are used in the settlement process. Prior to MHHS, this profiling assigns usage data across half-hour periods when actual data isn't available. Under MHHS, it will be replaced by Load Shapes, which draw on a far larger pool of similar consumers where half-hourly data is available to create more accurate load-shaping profiles data to estimate half-hourly usage.

 

Core migration window

The main period of transition to the MHHS system for business consumers, which begins in October 2025 for suppliers who qualified in the advanced cohort and runs until May 2027 (although most consumers will start the transition in May 2026).

 

Data Aggregator (DA)

Prior to the introduction of MHHS, a DA is appointed by a supplier to take validated meter data (from the Data Collector (DC)), convert it into energy volumes (measured in MWh) and send it to central settlement systems. Under MHHS, this specific role will be handled centrally as part of the new market design.

 

Data cleansing

The process of reviewing and cleaning data to ensure accuracy, prevent errors and reduce exceptions during migration.

 

Data Collector (DC)

Prior to the introduction of MHHS, a DC is appointed by a supplier to collect, validate and – where needed – estimate electricity consumption data from meters. Under MHHS, this role will gradually be replaced by the Smart Data Service (SDS) (for Smart and traditional meters), Advanced Data Service (ADS) (for Half-Hourly (HH) and Automated Meter Reading (AMR) meters) and the Unmetered Supplies Data Service (UMSDS) (for unmetered sites).

 

Data Communications Company (DCC)

The organisation responsible for managing the secure flow of data to and from Smart meters. It acts as the central communications link between Smart meters, suppliers and authorised agents. Under MHHS, the Meter Data Retriever (MDR) connects to the DCC to access Smart meter data for settlement.

 

Data Integration Platform (DIP)

This is the central messaging system within the MHHS operating model that allows different market participants – such as suppliers, agents and central services – to exchange information quickly and efficiently. It operates by publishing data files on an interface with market participants subscribing to updates, enabling their systems to obtain information (like meter readings or registration changes) in close to real time.

 

Demand forecasting

The process of predicting how much electricity will be needed in the future to meet expected consumption to each half-hourly settlement period, based on previous patterns in energy usage and other influencing factors such as the weather. Under MHHS, access to more detailed (half-hourly) data will help to improve the accuracy of these forecasts, supporting a more responsive and efficient energy system.

 

Direct meter read

A meter reading taken directly from the meter, either manually (on-site) or through an automated system. Under MHHS, direct meter reads are used whenever possible. But where they’re unavailable, estimates (like those from the Load Shaping Service (LSS)) may be used to fill the gaps.

 

Distribution losses

The amount of electricity that is lost as it travels through the local distribution network — due to heat loss or resistance in cables and transformers. These losses are estimated using Line Loss Factors (LLFs) and are factored into settlement to ensure suppliers are charged fairly for the energy delivered.

 

Distribution Network Operator (DNO)

DNOs own, operate, and maintain the distribution networks that carry power from the transmission system to homes and businesses. There are currently 14 licensed DNOs in Britain, each responsible for a specific region.

 

Dual-run

A period during the MHHS migration when both the preceding (i.e. legacy) settlement process and the new MHHS system operate in parallel. It helps to ensure a smooth transition by allowing issues to be identified and resolved before the new system takes over fully.

 

Elexon

The organisation responsible for delivering the MHHS programme. Elexon acts on behalf of Ofgem, the energy regulator who instigated MHHS, in coordinating the design and implementation of MHHS across the electricity industry.

 

Grid Supply Point (GSP)

A connection point where the electricity Transmission System connects to a Distribution System, representing the transition of electricity from the main higher-voltage transmission network to a local network.

 

Grid Supply Point (GSP) Group

A defined regional area of the UK that groups electricity consumption to manage settlement within that region. Each GSP Group links to one or more GSPs.

 

Half-Hourly (HH)

A method of measuring and recording electricity consumption every 30 minutes. It’s commonly used by larger business consumers and is a key part of MHHS, which will extend half-hourly settlement across the market.

 

Interface (IF) Flows

Introduced under MHHS, these are industry data messages exchanged through the Data Integration Platform (DIP) in a pre-defined structured data flow. They allow participants to create the specified data flow information ready for publication onto the DIP.

 

Line Loss Factor (LLF)

A calculation used to estimate how much electricity is lost as it travels through the local distribution network before reaching consumer sites.

 

Line Loss Factor Identifier (LLF ID)

A data item used to apply the correct Line Loss Factor when calculating how much electricity is lost as it travels through the network. This helps ensure accurate invoicing and settlement. Under MHHS, the LLF ID will be linked to the Distribution Use of System (DUoS) tariff ID to improve consistency and standardisation across the market.

 

Load Shape

A Load Shape is a pattern that shows the average electricity usage across a typical day, broken down by half-hour periods. Under MHHS, these shapes are generated by the Load Shaping Service (LSS) to help estimate energy usage when actual meter data isn’t available, especially for traditional meters.

 

Load Shaping Service (LSS)

The LSS creates average daily usage patterns (called Load Shapes) using actual half-hourly data. These patterns are used to estimate electricity use when actual meter readings aren’t available, especially for traditional meters. The aim is to make sure all customers can be settled using half-hourly data, even if their meter can’t provide it directly.

 

Market Segment

Under MHHS, consumers are grouped into one of three market segments – Smart, Advanced or Unmetered – based on domestic or non-domestic, connection and meter type and how their electricity usage is recorded. This segmentation determines which roles, data processes and settlement arrangements apply to each consumer.

 

Market Segment Code (A/U/S)

A single-letter code used in MHHS to indicate which market segment a consumer falls into: A (Advanced), S (Smart) or U (Unmetered). These codes help determine which roles and data processes apply to the consumer’s supply point.

 

Market Segment Identifier (Segment ID)

A new MHHS field that categorises a site based on how it's metered and settled. S – Smart, A – Advanced, U – Unmetered. Used alongside Connection Type to determine how a site is treated under MHHS rules.

 

Market-wide Data Service (MDS)

The MDS is a central service that checks and prepares electricity usage data for settlement. It brings together data from across the market – including Smart, Advanced, and Unmetered segments – and ensures it’s complete and accurate before it goes into the central settlement process.

 

Market-wide Half Hourly Settlement (MHHS)

MHHS is a major change to how electricity is settled in Britain. It uses half-hourly electricity usage data – often from Smart or advanced meters – to settle all consumers more accurately and efficiently. The goal is to create a smarter, more flexible energy market, supporting innovations like time-of-use tariffs and demand forecasting.

 

Measurement Class (MC)

A category that describes how electricity consumption is measured at a site. For example, whether it's Half-Hourly (HH) or Non-Half Hourly (NHH) and whether the supply is metered or unmetered. This has been used to determine how data is processed for settlement.

 

Under MHHS, the MC is being phased out and replaced by Connection Type and Market Segment Identifier, which provide a more accurate view of how a site is configured and settled. Example codes include:

A – Non-Half Hourly (NHH) metering

B – NHH Unmetered Supplies (UMS)

C – Half-Hourly (HH) metering at sites >100 kW

D – HH UMS

E/F/G – HH metering at smaller sites (<100 kW)

 

Meter Administrator (MA)

A role responsible for managing unmetered consumption data, including calculating usage based on equipment inventories. Under MHHS, this role will be replaced by the Unmetered Supplies Data Service (UMSDS), which provides settlement-ready data for unmetered sites such as street lighting and traffic signals.

 

Meter Data Retriever (MDR)

Part of the Smart Data Service (SDS), the MDR connects to the Data Communications Company (DCC) to retrieve electricity usage data from Smart meters. This data is then passed on for processing and settlement under MHHS. Suppliers can either carry out this role themselves or appoint a third party MDR provider.

 

Meter Operator (MOP)

A party appointed by a supplier to install, maintain and repair electricity metering equipment. Under MHHS, the MOP role is replaced by the Metering Service (MS) roles — either Metering Service Advanced (MSA) or Metering Service Smart (MSS), depending on the type of meter.

 

Meter Point Administration Number (MPAN)

A unique 21-digit number used to identify an electricity supply point in Great Britain. You may also hear it referred to as a Supply Number or S-Number. It’s used across the industry to manage switching, settlement and other meter-related processes.

 

Meter Reading Service (MRS)

Under MHHS, the MRS obtains meter register readings for meters where Settlement Period Level data is not available or cannot be accessed from meters in the Smart and Non-Smart market segments (e.g. for traditional meters).

 

Meter Timeswitch Code (MTC)

A three-digit code that identifies how a meter is set up to record electricity usage. For example, whether it uses multiple registers for day and night rates. Under MHHS, the MTC is replaced with the Standard Settlement Configuration (SSC) in the top-line of the Meter Point Administration Number (MPAN) to improve visibility of optional invoicing registers for consumer switching.

 

Metering Service (MS)

A new MHHS role that replaces the traditional Meter Operator (MOP). MS providers are responsible for installing, maintaining and managing electricity meters. Under MHHS, there are different types of MS roles depending on the meter type – for example, Metering Service Advanced (MSA) and Metering Service Smart (MSS).

 

Metering Service Advanced (MSA)

The MSA is the MHHS role responsible for installing, maintaining and managing advanced meters (typically Half-Hourly (HH) and Automated Meter Reading (AMR) meters). It replaces the traditional Meter Operator (MOP) role for consumers in the Advanced Market Segment.

 

Metering Service Provider (MSP)

A general term for an agent responsible for metering services including installation, maintenance and configuration of meters. Under MHHS, this includes roles such as Metering Service Advanced (MSA) and Metering Service Smart (MSS), depending on the meter type.

 

Metering Service Smart (MSS)

The MSS is the MHHS role responsible for installing and maintaining Smart meters and traditional (non-Smart) meters that fall within the Smart Market Segment. It replaces the Meter Operator (MOP) role for consumers in this segment.

 

Migration Control Centre (MCC)

A central team overseeing the migration of Meter Point Administration Numbers (MPANs) to MHHS. The MCC approves migration batches, monitors progress and supports suppliers and agents during the transition.

 

Office of Gas and Electricity Markets (Ofgem)

Ofgem is the regulator for energy in Great Britain and is responsible for protecting the interests of gas and electricity consumers and ensuring the market works fairly and efficiently. Ofgem is overseeing the delivery of MHHS and has appointed Elexon as the programme’s delivery body.

 

Processing Service (Smart) (PSS)

Under MHHS, the PSS is a key component of the Smart Data Service (SDS), responsible for validating and estimating raw meter readings to create settlement-period-level consumption data. It uses load profiles for non-smart and Profile Class consumers to estimate their consumption, ensuring accurate settlement for all electricity users by transforming raw data into usable consumption profiles for suppliers.

 

Profile Class

Eight different categories for consumers with traditional (Non-Half Hourly (NHH)) meters, allocated according to consumption pattern and premises type. Under MHHS, these will remain as mandatory allocations for traditional meters, and may also be used for advanced and Smart meters if suppliers deem appropriate. The load profiles that go with each class will be replaced by far more granular Load Shapes to generate half-hourly data to support more accurate settlement.

 

Publish Flows (PUB flows)

Introduced under MHHS, these flows publish data via the Data Integration Platform (DIP), making it available to all relevant market participants without needing to send messages directly to each one.

 

Radio Teleswitch Service (RTS)

A service provided by the Energy Networks Association (ENA) to Elexon to transmit radio signals that control teleswitch meters. These meters respond to radio signals to switch between tariffs (e.g. day and night rates). RTS is being phased out and consumers with RTS meters are transitioning to more modern meter technologies.

 

Reading frequency

A data item that indicates how often meter readings are expected. Under MHHS, codes like M (Monthly), Q (Quarterly) and A (Annually) may be used to describe expected reading intervals.

 

Registration Service (RS)

This is a system managed by each local Distribution Network Operator (DNO) to store key data about each electricity supply point (Meter Point Administration Number (MPAN)) connected to their networks. It supports how the industry tracks and manages meter points, and includes who the supplier is, which agents are appointed, the type of meter and consumer, and other important details used for settlement.

 

Reverse migration

A fallback process used during the initial phase of MHHS to allow a consumer who has already migrated to the new MHHS model with their current supplier to switch to a new supplier, who has not yet qualified under MHHS.

 

Settlement

The process of matching how much electricity consumers use with how much is generated, so that suppliers can be invoiced accurately for customer consumption and total generation and consumption can be balanced across the whole electricity system. MHHS aims to improve this process by using more detailed, half-hourly data to make settlement faster and more precise.

 

Smart and Non-Smart Segment

This is one of the three market segments under MHHS and includes Smart meters (whether they send half-hourly data or just register readings) and traditional (i.e. non-Smart) meters that do not send data automatically. Data from this segment is managed by the Smart Data Service (SDS).

 

Smart Data Service (SDS)

A key MHHS role that handles the collection, validation and preparation of electricity usage data from meters in the Smart Market Segment, including both Smart and traditional (non-Smart) meters. The SDS ensures that data is ready for half-hourly settlement and replaces the traditional Data Collector (DC) role for these consumers.

 

Smart Data Service Provider (SDSP)

An agent appointed to carry out functions within the Smart Data Service (SDS) under MHHS.

 

Smart meter

A meter which is compliant with the Smart Metering Equipment Technical Specifications (SMETS). In addition to measuring and registering the amount of energy that passes through it, a Smart meter is capable of additional functionality such as recording consumption/export in each half hour of the day and of being remotely read and configured.

 

Standard profile curves

A set of predefined patterns used to estimate how electricity is typically used throughout the day for different types of consumers. They are used in Non-Half Hourly (NHH) settlement when actual usage data is not available. These curves are being phased out under MHHS in favour of more accurate half-hourly data.

 

Standard Settlement Configuration (SSC)

A standard metering system configuration recognised by the supplier. Under MHHS, this will no longer be relevant to settlement processes, but will be retained to allow suppliers to understand the meter configuration for optional invoicing purposes.

 

Standard Settlement Configuration Identity (SSCID)

A unique identifier for a specific Standard Settlement Configuration (SSC) under MHHS. It supports automation by linking a meter's setup (registers and time patterns) to the correct settlement process.