MHHS Glossary
Purpose:
The shift to Market-Wide Half-Hourly Settlement (MHHS) has introduced a wave of new terms, codes, and acronyms that can be confusing for businesses and consumers alike. We have put together this glossary to explain the MHHS terms in an easy-to-understand way, so you always know what is happening with your electricity supply. Whether you are reviewing your bills, speaking to your supplier, or preparing for meter migration, this guide is here to help you stay informed every step of the way.
| Terms | Definition |
|---|---|
| MHHS (Market-Wide Half-Hourly Settlement) | A major UK energy reform that measures your electricity use every 30 minutes instead of relying on estimates, giving you more accurate bills and new tariff options. |
| Advanced Data Service (ADS) | The new specialist service that collects and processes electricity data from advanced meters like HH and AMR meters. It replaced the old Data Collector role. |
| Advanced Market Segment | The market group in which half-hourly data from advanced meters is used for settlement. Even if the meter cannot communicate, it stays in this group. |
| Advanced Meter | A meter that automatically records your electricity use every 30 minutes and sends that data to your supplier, no manual reads needed. |
| Agent Appointments | When your supplier assigns specialist companies to look after your metering and data services. The types of agents and their roles changed under MHHS. |
| Annual Consumption (AC) | Replaced the old Estimated Annual Consumption figure. It is the expected amount of electricity your site will use in a year, based on more accurate data than before. |
| Central Switching Service (CSS) | The national system that manages all electricity supplier switches across Great Britain, making sure handovers between suppliers are smooth and accurate. |
| Change of Agent (CoA) | When your supplier swaps one of the specialist companies managing your meter or data services for another. MHHS introduced stricter rules around this to keep your data accurate. |
| Change of Supplier (CoS) | When you move from one electricity supplier to another. MHHS makes this process quicker and more accurate thanks to better data being available. |
| Clean Power 2030 | The UK government's target is to have a fully clean electricity system by 2030. MHHS is one of the major building blocks to get there by making the grid smarter and more responsive. |
| Connection Type | A code describing how your site physically connects to the electricity network. It determines what type of meter can be installed at your premises. |
| Consumption Profiles | Estimates of how a typical customer uses electricity across the day, split into half-hour slots. Under MHHS, these are being replaced by more accurate Load Shapes. |
| Migration Window | The main period when suppliers are moving customers over to the new MHHS system. It runs from October 2025 through to May 2027. |
| Data Aggregator (DA) | The old pre-MHHS role that converted validated meter data into energy volumes for central settlement. This function is now handled centrally under MHHS. |
| Data Cleansing | The process of checking and correcting your meter data to make sure it is accurate before it is used in settlement is especially important during migration. |
| Data Collector (DC) | The old pre-MHHS role that collected and validated your electricity consumption data. Now replaced by the SDS, ADS, or UMSDS, depending on your meter type. |
| Data Communications Company (DCC) | The organisation that manages the secure flow of data between smart meters and suppliers. Think of them as the secure postal service for your meter readings. |
| Data Integration Platform (DIP) | The new central messaging system that lets suppliers, agents, and central bodies share information quickly and in near real time under MHHS. |
| Direct Meter Read | A reading taken straight from your meter, either by a site visit or through an automated system. MHHS prefers direct reads; estimates are only used when unavoidable. |
| Distribution Losses | A small amount of electricity is lost as heat, travelling through cables and transformers to your premises. These losses are factored into the settlement, so suppliers are charged fairly. |
| Distribution Network Operator (DNO) | The company is responsible for the local electricity network in your area. There are 14 regional DNOs in Great Britain; they own the cables that bring electricity to your door. In MHHS, called LDSO. |
| Distribution Use of System (DUoS) Tariff ID | The new code on your bill replaced the old-Line Loss Factor. It reflects the cost your supplier pays to use the local distribution network to deliver electricity to your site. |
| Elexon | The organisation appointed by Ofgem to deliver the MHHS programme. They coordinate the industry and oversee all the technical changes needed to make MHHS work. |
| Estimated Annual Consumption (EAC) | The old way of estimating how much electricity your site uses in a year. Replaced by Annual Consumption (AC) under MHHS, which uses more accurate real-world data. |
| Grid Supply Point (GSP) | Where the main high-voltage national transmission network connects to your local distribution network. Electricity flows through GSPs on its way down to homes and businesses. |
| Half-Hourly (HH) Meter | A meter that records your electricity use every 30 minutes. Larger business sites have typically had these for years. MHHS extends this approach to all consumers. |
| Line Loss Factor (LLF) | The calculation used to account for electricity lost as it travels through the local network. Previously shown on your bill and MPAN top line, now replaced by the DUoS Tariff ID. |
| Load Shape | A detailed pattern showing average electricity usage across each half-hour of the day for a specific type of consumer. Used in MHHS instead of old profile classes to produce more accurate settlement estimates. |
| Load Shaping Service (LSS) | The central service that generates Load Shapes using real half-hourly data from large numbers of similar consumers. It fills the gaps for sites where actual half-hourly readings cannot be obtained directly. |
| Market Segment | Under MHHS, every electricity supply point is placed into one of three segments: Smart, Advanced, or Unmetered, which determines which services and settlement rules apply to you. |
| Measurement Class (MC) | A code describing how your electricity was measured and settled. Being replaced under MHHS by Connection Type and Market Segment Identifier. |
| Meter Data Retriever (MDR) | The part of the Smart Data Service that connects to the DCC to pull readings directly from your smart meter. Your supplier can do this themselves or appoint a specialist. |
| Meter Operator (MOP) | The old pre-MHHS role was responsible for installing and maintaining your electricity meter. Replaced by either MSA or MSS under MHHS, depending on your meter type. |
| Meter Point Administration Number (MPAN) | Your unique 13-digit electricity supply number, sometimes called your Supply Number or S-Number. It identifies your specific supply point and appears on your energy bills. |
| Meter Reading Service (MRS) | Under MHHS, the service that obtains actual meter register readings from sites where half-hourly data cannot be retrieved automatically, such as traditional meters. |
| Meter Timeswitch Code (MTC) | The old three-digit code on your MPAN describes how your meter was set up, for example, whether it recorded separate day and night rates. Replaced by the SSC under MHHS. |
| Metering Service (MS) | The new MHHS name for what used to be the Meter Operator role. MS providers install, maintain, and manage your meter under the new arrangements. |
| Metering Service Advanced (MSA) | The MHHS role that looks after advanced meters, including HH and AMR meters. Replaced the old Meter Operator role for customers in the Advanced Market Segment. |
| Metering Service Smart (MSS) | The MHHS role that looks after smart meters and traditional non-smart meters in the Smart Market Segment. Replaced the old Meter Operator role for these customers. |
| Net Zero | The UK's commitment is to cut greenhouse gas emissions as close to zero as possible. MHHS supports this by enabling a smarter, more flexible electricity grid that makes better use of renewable energy. |
| Office of Gas and Electricity Markets (Ofgem) | The regulator for gas and electricity markets in Great Britain. Ofgem instigated MHHS and appointed Elexon to deliver it. Their job is to make sure energy markets work in the interests of consumers. |
| Peak Demand | The times when electricity use across the grid is at its highest, typically weekday evenings. MHHS encourages customers to shift usage away from these peak hours, which can lower bills and help balance the grid. |
| Profile Class | The old system grouped customers into one of eight categories based on consumption patterns and premises type. Being replaced by more accurate Load Shapes under MHHS. |
| Radio Teleswitch Service (RTS) | A legacy system that sent radio signals to older meters to switch them between tariff rates, such as Economy 7-day and night rates. RTS is being phased out, and customers need to upgrade to a modern meter. |
| Registration Service (RS) | The Registration Service is a central database that holds information about every electricity supply point (MPAN) in a given area. It keeps a record of who your current supplier is, which metering and data agents are appointed to your site, what type of customer you are, and technical details such as how your meter is classified and whether your supply is active. |
| Smart Data Service (SDS) | The MHHS service is responsible for collecting, validating, and preparing electricity data from smart and traditional meters. It replaced the old Data Collector role for these customers. |
| Smart Metering Equipment Technical Specifications (SMETS) | The technical standards smart meters must meet in Britain. A SMETS-compliant meter can record half-hourly usage and be read remotely, exactly what MHHS requires. |
| Standard Settlement Configuration (SSC) | The four-digit code replaced the old three-digit Meter Timeswitch Code on your MPAN top line. It describes how your meter is configured for invoicing purposes. |
| Supply Number (S-Number) | Another name for your MPAN is the unique reference number for your electricity supply point, found on your energy bills and contracts. |
| Target Operating Model (TOM) | The overall design of how the MHHS electricity market will work once migration is fully complete, covering all new roles, services, data flows, and settlement arrangements. |
| Time-of-Use Tariff | A type of tariff where you pay different prices depending on when you use electricity. MHHS makes these widely available, giving businesses the chance to save money by shifting usage to cheaper off-peak times. |
| Unmetered Supplies (UMS) | Electricity supplies without a physical meter on site, such as street lighting, traffic signals, or CCTV. Settled under MHHS using equipment inventories and usage estimates. |
| Unmetered Supplies Data Service (UMSDS) | The MHHS service that handles settlement data for unmetered sites, like street lighting and traffic lights. Replaced the old Meter Administrator role. |