Identifiers and registers: MPAN, MPRN and the system's spine

An MPAN is not a serial number. It is a bundle of market decisions wearing a serial number. That single sentence is the whole point of this section, and it is the reason a course on energy system data has to teach identifiers before it teaches anything about flows, settlement or open data. Every record in the GB electricity retail estate is keyed on the MPAN, and the identifier itself carries settlement instructions that other systems read and act on.

The electricity Meter Point Administration Number is 21 digits, printed in two rows. The lower row of 13 digits is the core, and it is the part a supplier will ask you for. The upper row of 8 digits carries the settlement configuration. Read them in order and the identifier tells you how the meter point is treated, not merely which meter point it is.

• Profile class (2 digits, top line). A profile class says how the meter point's consumption is shaped across the day when there is no half-hourly measurement to use. Class 00 marks a meter point already settled half-hourly; the numbered domestic and non-domestic classes above it map onto standard load shapes.
• Meter time-switch code (3 digits, top line). Describes the switching arrangement of the metering equipment: single rate, multiple rates, a time-switched register set, and so on. It tells a data collector how many registers to expect and what each one means.
• Line loss factor class (3 digits, top line). The line loss factor class is set by the distribution network operator. It selects the multiplier applied to metered volume so that losses between the grid supply point and the premises are accounted for, and it is also the hook that distribution charges hang on.
• Distributor identifier (2 digits, core). Says which DNO allocated the MPAN and is responsible for maintaining its technical detail.
• Unique identifier (10 digits, core). The part that is genuinely only an identifier. It is unique within the distributor, not nationally, which is why the distributor identifier has to sit in front of it.
• Check digit (1 digit, core). Derived from the preceding digits of the core so that a transposed or mistyped MPAN fails validation at the door instead of creating a plausible but wrong record deep inside a settlement system.

Gas is structurally simpler. The MPRN, sometimes called the M number, is a plain numeric identifier of up to ten digits for a gas supply meter point. It carries no profile class, no time-switch code and no loss factor class. The gas equivalents of those settlement attributes are held as separate fields in the central gas systems rather than encoded in the identifier itself. This is a useful contrast to hold: the electricity industry pushed settlement metadata into the key, and the gas industry did not.

That design choice has consequences. Because settlement attributes live inside the electricity identifier, changing how a meter point is settled means changing part of its MPAN record, and every party holding a cached copy has to be told. Because they live outside the gas identifier, an MPRN is stable but tells you almost nothing on sight. Neither approach is better in the abstract; each simply moves the cost to a different place.

The collective term for both is MPXN, and you will see it wherever a document has to talk about a meter point without committing to a fuel. Switching messages, address records and consent records all use it. The takeaway from this section is that an identifier in GB energy is a compressed contract: it names a point on the network, and in electricity it simultaneously instructs the market how to treat what happens there.

A house with solar panels does not have one meter point with a number that goes up and down. It has two meter points. The import MPAN records energy taken from the network, and a separate export MPAN records energy delivered back to it. They are distinct registrations, they can be held by different parties, and they are settled through different routes.

This is the single most common misunderstanding in GB retail energy data, and it is worth being blunt about the correct model. Import and export are separate registers. Consumption never goes negative. If you are looking at a consumption series and you see a negative value, you are not looking at a house exporting; you are looking at a data quality problem, a register that has been read in the wrong direction, or an export series that has been mislabelled as import.

The practical consequences show up immediately. A supplier billing a solar household needs both series and has to keep them apart: charge for import, credit for export, and never net them inside a single register. A payment under the Smart Export Guarantee is made against export volume, which means an export meter point has to exist and be registered before any payment can be calculated. A household that installs generation and never gets an export MPAN allocated has, from the market's point of view, not exported anything at all, regardless of what the inverter says.

What breaks when the export MPAN is missing is instructive. The generation is still physically flowing into the local network, so the distributor sees it in aggregate. The volume has to be reconciled somewhere, so it lands in the unallocated residue that the settlement process has to spread across other parties. The household loses its export payment. The supplier cannot evidence the export. Nobody in the chain has done anything wrong; a register entry simply does not exist, and everything downstream degrades quietly rather than failing loudly.

Note the family relationship. Import meter point, export meter point, and in gas the single supply meter point, are all instances of the same concept: a registered point where energy crosses a boundary and is measured. MPXN is the name for that concept. Module 11 returns to export in depth, including the Smart Export Guarantee and the data chain behind microgeneration payments. What you need from this module is the structural fact that export is a first-class object with its own identifier, not an adjustment to an import number.

A grid supply point is a physical thing. It is a substation where the transmission network hands electricity down to a distribution network, and there are several hundred of them across Great Britain. A GSP Group is an accounting region. There are exactly 14, they are identified by letters, and they are the level at which settlement volumes are reconciled and at which most regional energy data products are published.

Confusing the two is not a harmless slip. It produces a specific class of error: the belief that there are 14 physical handover points between transmission and distribution in GB, which would make the network far simpler than it is. The many grid supply points inside a region roll up into one GSP Group; the group is the container, the supply point is the equipment.

The reason the two-level structure exists is boundary metering. Each grid supply point is metered where the transmission and distribution networks meet, and those meters measure the total energy entering the distribution region. That total is the truth the settlement process has to reconcile against. Add up everything suppliers claim their customers consumed inside the region, add the estimated losses, and the result should match what the boundary meters recorded. It never matches exactly, and the gap has to be allocated.

This is why the GSP Group, not the individual supply point, is the unit of settlement. Reconciling at each of several hundred supply points would be pointless precision: customers are registered to suppliers, not to substations, and a supplier's portfolio inside a region is spread across many supply points. Aggregating to 14 groups gives a boundary that is both physically meaningful, because it is measured, and commercially meaningful, because it is the level at which supplier positions can be compared.

The GSP Group identifier is also the join key for a large amount of published regional data. Regional demand profiles, regional loss factors and regional price components are all published by group. If you are building anything that compares regions in GB electricity, the GSP Group letter is almost certainly the column you will join on, and the number of distinct values you should expect is 14.

One caution before moving on: GSP Group boundaries are not the same as DNO licence areas, local authority boundaries or postcode areas, even though several of them look similar on a map. Treating any of those as interchangeable will produce results that are subtly wrong in the places where the boundaries diverge, which tends to be exactly the edge cases an analysis is trying to explain.

An identifier is only useful if something authoritative knows what it points at. Whoever runs that authoritative record controls the market's memory, and in GB the memory is split across a small number of named systems. The most important question a register answers is the simplest one: who supplies this meter point today?

Since July 2022 the answer comes from the Central Switching Service. The CSS is the registration source of truth for both electricity and gas, it is operated by the DCC, and it sits under the Retail Energy Code with RECCo as the code body. Before CSS, electricity and gas registration ran on separate arrangements with different timescales and different failure modes. Putting both fuels behind one registration service is the reason a modern switch completes in days rather than weeks.

• Central Switching Service (CSS), operated by the DCC under the REC. Holds the registration: which supplier is registered to which MPXN, and from when. This is the register that answers the who-supplies-this question for both fuels.
• The Retail Energy Location record, governed under the REC. Retail Energy Location is the shared address record that ties MPXNs to a consistent view of premises. It is the asset the RECCo and DCC improvement plan in the story above is aimed at, because address mismatch is where switching goes wrong.
• MPAS, the meter point administration heritage. Each DNO has long run a Meter Point Administration Service that allocates MPANs and maintains their technical attributes: distributor identifier, line loss factor class, connection details. Registration moved to CSS; MPAN allocation and technical maintenance did not. Both records exist, and they have to agree.
• UK Link on the gas side, the central gas system operated by Xoserve on behalf of the gas transporters. It holds the supply point record behind each MPRN, including the attributes that electricity chose to encode in the identifier.
• Meter serial numbers, held against the meter point rather than being the meter point. A meter is replaced; the MPXN persists. Confusing the asset identifier with the meter point identifier is a reliable way to lose a customer's history at the moment their meter is exchanged.

Two structures in that list are on their way out, and you should learn them as legacy rather than as current design. Profile classes and standard settlement configurations exist because the market needed a way to shape and settle consumption at meter points that were not measured half-hourly. Under Market-wide Half-Hourly Settlement, actual half-hourly data replaces the estimated shape, so the profile class becomes a field that describes the past rather than one that drives a calculation. Expect to keep meeting it in historical data and in systems that have not finished migrating, and expect it to stop carrying meaning.

The wider point, and the reason this module sits early in the course, is that identifier quality is a market-wide cost rather than a back-office one. A wrong address in the location record causes a failed or erroneous switch. A missing export MPAN costs a household its export payment and leaves volume unallocated in settlement. A meter point whose line loss factor class is wrong is charged the wrong distribution costs for as long as nobody notices. None of those are visible as data problems when they surface. They surface as billing complaints, as disputed settlement runs, and as regulatory attention. The register is where they start.