The Great Britain energy data layer in May 2026: six sub-domains from actors and roles to CIM and interoperability

Sub-domain 1: Actors and roles across the GB energy data layer, with the global comparison absorbed

Every dataset in the GB energy data layer has a producer (a meter, a telemetry feed, a publication routine inside a licensee), a custodian (the body that owns the storage, the metadata and the publication cadence), and a consumer (the analyst, settlement engine, planner or member of the public reading it). The actors-and-roles sub-domain names every party on every flow so a reader does not have to reconstruct who is responsible for what across forty bilateral pairings in their head. The previous workspace also kept a separate global-comparison sub-domain that placed GB next to the EU CGMES regime, the US ISO and RTO data publication regimes, the Australian National Electricity Market data hub and the Nordic Nordpool data exchange; the master plan absorbs that comparison into this sub-domain because it reads as one continuous question with the GB actors list (who plays each role here, and who plays it abroad).

The actors split into seven groups. The first group is the policymaker. DESNZ owns the framework documents that bind every other actor: the Energy Smart Data and Privacy Framework, the digital spine feasibility work, the Energy Digitalisation Strategy and Action Plan.¹⁴ The second group is the regulator. Ofgem grants and amends the licences under the Electricity Act 1989; Standard Licence Condition 25 of the Electricity Distribution Licence is the parent of the Long Term Development Statement, and 25.2 specifically requires publication at intervals of not more than seven years.^{12 13} Ofgem is the licence-amendment body when a new data publication obligation lands on a DNO or a TO; the LTDS Direction of 30 April 2024 is the most recent example, mandating the move from Excel files to a validated CIM data model.¹

The third group is the system operator. NESO has been running for nineteen months under the Energy Act 2023 and produces or convenes the Future Energy Scenarios, the Strategic Spatial Energy Plan, the Centralised Strategic Network Plan, the Grid Code change proposals (GC0139 for whole-system planning-data exchange among them), and the Connections Reform Gate 2 dataset that progressed 283 gigawatts of generation and storage in April 2026. The fourth group is the settlement administrator. Elexon runs the Balancing and Settlement Code, including the BSC P408 settlement run that turns 1.6 billion daily half-hourly observations into a daily settlement balance after MHHS cuts over in July 2027. The fifth group is the network licensees. The three transmission owners (National Grid Electricity Transmission, SP Transmission, SSEN Transmission) plus the fourteen distribution licence areas across six DNO groups publish the LTDS, the Network Development Plans, and the asset-register data that feeds CSNP through GC0139.

The sixth group is the data and code bodies. Smart DCC owns the Smart Energy Code communications hub that carries every SMETS2 meter message; the Retail Energy Code Company owns the Central Switching Service for supplier switching and the data flows that follow it; SECCo owns the Smart Energy Code itself; the Data Communications Company operates the DCC infrastructure under SEC Section L; BSI owns the CIM engagement portal at https://cim.bsigroup.com/ which runs the GB engagement on CGMES 3, IEC 61968-13 and IEC 61970-301.⁴ The seventh group is the consumer-facing actors. Suppliers hold the retail relationship with the consumer; price-comparison services, advice services, fuel-poverty bodies and consumer-advocacy bodies (Citizens Advice, the Energy Ombudsman, Energy UK, Energy Action) sit on top of the supplier flow.

The global comparison adds a single row to each actor group. The EU plays the policymaker, regulator and standards roles through DG ENER, ACER and the ENTSO-E and ENTSO-G associations; CGMES is the EU standard that GB has adopted for the LTDS. The US plays the same roles through the Department of Energy, FERC and NERC, plus the regional ISOs and RTOs (PJM, MISO, ERCOT) which run state-by-state market and settlement systems; the US data publication regime is fragmented by state. Australia plays them through the Australian Energy Market Commission, the Australian Energy Regulator and AEMO which runs the National Electricity Market and the AEMO Data Dashboard. The Nordics play them through the four national TSOs (Statnett, Svenska Kraftnät, Fingrid, Energinet) and Nord Pool which runs the regional wholesale exchange. The comparison matters because the GB choice of CGMES 3 for the LTDS aligns GB with the EU standard, which lowers the cost of cross-border model exchange through the interconnectors and gives GB analysts a shared schema with their EU counterparts.

The actors-and-roles sub-domain is the entry point because every other sub-domain is defined by which actor produces and which consumes the data flow inside it. A reader who arrives wanting to know who is responsible for the SSEP publishing schedule reads this sub-domain first to find NESO with DESNZ; a reader who arrives wanting to know who governs the SMETS2 meter data flow finds Smart DCC under SECCo and the Data (Use and Access) Act 2025. The sub-page treats every flow in the data layer with the producer, custodian and consumer named on it.⁸

Sub-page anchor: Actors and the related Global comparison page. Both sub-pages are at first-draft quality and queued for a follow-up rewrite to merge them into a single gold-standard actors-and-roles page per the master plan §E.4 consolidation.

Sub-domain 2: Physical data generation and the 87 named data types, with the taxonomy absorbed

The physical-data-generation sub-domain covers where the bytes come from. Every data flow in the GB energy data layer begins as a physical measurement, a telemetry packet or a publication routine running inside a licensee. The sub-domain names the device, the protocol, the volume and the frequency for each one, then collects them into the 87 named data types that the previous workspace held as a separate taxonomy page; the master plan absorbs the taxonomy because the named data types only make sense once the physical sources behind them are visible.

The largest single source of bytes is the SMETS2 smart meter fleet. Around 35.9 million domestic and small non-domestic electricity and gas meters are in the field as of early 2026, of which about 33 million are SMETS2 (the second-generation specification under the Smart Energy Code). Each meter takes a half-hourly reading and pushes it to the DCC over the SMETS2 communications hub. The half-hourly volume after MHHS cutover in July 2027 is 33 million MPANs times 48 half-hourly observations per day, which is around 1.6 billion observations per day or 583 billion per year flowing through the settlement chain.⁹ Before MHHS cutover, only a few million meters on a Time of Use tariff publish half-hourly data; the rest publish daily.

The second source is transmission and distribution SCADA telemetry. Each substation produces a stream of voltage, current, power, frequency and tap-position telemetry at one-second to one-minute intervals; PMUs (Phasor Measurement Units) at the transmission level produce thirty to sixty samples per second of voltage and current phasor data tagged with a GPS timestamp. The telemetry data does not leave the licensee in normal operation; it is the operational substrate that NESO and the TO use to manage the system in real time, and it feeds the Energy Balancing Service Adjustment Data that publishes after each settlement period through BMRS.

The third source is the wholesale market data. The Elexon Balancing Mechanism Reporting Service (BMRS) publishes physical notifications, final physical notifications, bid-offer acceptances, system buy and sell prices, system frequency, and settlement period imbalance volumes at half-hourly cadence under the BSC. The data is downloadable from BMRS in real time and is the canonical source for any market-facing analyst.

The fourth source is the connections and asset data. The LTDS, the Embedded Capacity Registers, the Long Term Development Statement, the Distribution Future Energy Scenarios published by each DNO, and the Network Development Plans together describe the asset state, the contracted load and generation, and the planned reinforcement at every substation in GB. From 29 May 2026 the LTDS publishes in CIM format under the third Ofgem derogation letter; the volume per Stage 2 publication is around 500 megabytes per DNO across the CGMES profiles, with mRIDs (master resource identifiers) tying each topology element to a stable identifier across publication cycles.

The fifth source is the policy-modelling data. DESNZ publishes the Energy and Emissions Projections, the Digest of UK Energy Statistics (DUKES), the Sub-national Energy Consumption statistics, and the Future Energy Scenarios that NESO produces with DESNZ. These datasets feed every policy projection, planning scenario and ministerial briefing.

The taxonomy collects all of these into 87 named data types across 13 categories. The categories are: meter readings; settlement; balancing; capacity; connections; asset register; topology; tariffs; emissions; demand; generation mix; markets; and modelling. Each named type carries its licence (Crown Copyright, NESO Open Licence, CC BY 4.0, restricted, commercial), its custodian (the licensee or body that owns it), its consumer set (the actors that read it), and its publication cadence (real-time, half-hourly, daily, monthly, quarterly, annual). The taxonomy is the catalogue a planner uses when asked for "the data on X"; it converts a casual question into a named row in the catalogue with a custodian, a licence and a cadence beside it. The Energy Smart Data and Privacy Framework treats the taxonomy as the inventory it scopes its smart-data provisions over.¹⁴

Sub-page anchor: Smart meters, Network telemetry, and Data types catalogue. The three pages are at first-draft quality and queued for a follow-up rewrite to merge them into a single gold-standard physical-data-generation page per the master plan §E.4.

Sub-domain 3: Lifecycle and settlement, from a meter reading to a consumer bill

The lifecycle-and-settlement sub-domain walks a single half-hourly observation through the data chain from the meter on the wall to the settlement run at Elexon to the line item on a consumer bill. The half-hour is the canonical settlement period under the Balancing and Settlement Code; everything in the GB electricity market settles in half-hourly intervals, and the MHHS programme is the move to make that true for every meter rather than only for the Time of Use minority.⁹

The lifecycle has eight stages. Stage one is measurement. A SMETS2 electricity meter takes a half-hourly active import reading at the close of each half-hour and stores it in volatile memory. Stage two is local validation. The meter checks the reading against its own clock (synchronised through the SMETS2 communications hub) and produces a signed observation. Stage three is transport. The DCC carries the observation over the SMETS2 communications hub from the meter to the registered Supplier, the Distribution Network Operator that owns the local network, and any other authorised party (Time of Use tariff providers, in-home display routers). Stage four is supplier ingestion. The supplier ingests the half-hourly read into its billing engine and applies the active tariff to compute the consumer-side cost of the half-hour.

Stage five is settlement aggregation. The supplier submits the half-hourly aggregated meter data to Elexon under the BSC. Stage six is the settlement run. Elexon runs the half-hourly settlement under BSC Section S; the run computes the settlement-period imbalance volume for each balance responsible party (typically a supplier or a generator) and publishes the result. BSC P408 was the modification approved in November 2022 that defined the post-MHHS settlement run; the algorithm runs over the half-hourly reads from the central settlement system rather than the profiled non-half-hourly reads that were the pre-MHHS norm.

Stage seven is the reconciliation. The Initial Settlement Run is followed by the R1, R2, R3, RF and DF reconciliation runs at progressively longer intervals (R1 at fourteen calendar days, R2 at four months, R3 at fourteen months, RF at twenty months, DF at twenty-eight months); each reconciliation run corrects for late-arriving meter data and disputed readings, with the final DF run being the binding settlement. Stage eight is the consumer bill. The supplier issues the bill to the consumer (monthly, quarterly or annual depending on the tariff) showing the energy charge (computed from the tariff and the metered consumption), the standing charge, network charges (passed through from the DUoS and TNUoS published by the DNO and the TO), the Renewables Obligation pass-through, the Climate Change Levy on non-domestic supplies, and VAT.

Two reforms reshape this lifecycle in the period the workspace covers. The first is MHHS. Migration began on 22 October 2025; Milestones M10 to M13 in early 2026 represent ten million MPAN initiations into the new central settlement system; the programme cuts over at Milestone M16 in July 2027, after which every half-hourly observation flows through the BSC P408 settlement run for every meter rather than for the Time of Use minority. The data volume change is large: the central settlement system processes 1.6 billion observations per day after cutover rather than the few hundred million it processes today.⁹

The second reform is the Energy Smart Data and Privacy Framework. DESNZ published the framework in March 2026 as the policy framework for the energy-smart-data scheme that the Data (Use and Access) Act 2025 enables; the framework sets the rules for how a consumer authorises a third party (a price-comparison service, an advice service, a tariff-switching service) to read the consumer's half-hourly data and act on it on the consumer's behalf.¹⁴ The framework is the consumer-side counterpart to MHHS: MHHS makes the half-hourly data exist for every meter; the framework defines how a consumer can authorise the use of that data for a service.

The lifecycle sub-page treats each of the eight stages with the data formats, the message types, the publication cadence and the BSC modifications that govern it. The sub-page also tracks the BSC modification log so a reader can see which modifications are currently in flight and what they would change in the lifecycle if they progress.

Sub-page anchor: Lifecycle and settlement. The page is at first-draft quality and queued for a follow-up rewrite to bring it to gold standard per the master plan §E.4.

Sub-domain 4: Rules and governance after the Data (Use and Access) Act 2025

The rules-and-governance sub-domain covers the legal and licence framework that binds every flow in the data layer. The substrate is the Data (Use and Access) Act 2025. Royal Assent was 19 June 2025. Two Commencement Orders in February 2026 brought the operative provisions into force: SI 2026/31 (Commencement No. 5) brought Section 138 into force on 6 February 2026, and SI 2026/82 (Commencement No. 6) brought the majority of Part 5's data-protection provisions into force on 5 February 2026.^{8 16 17} Part 5 amends the UK General Data Protection Regulation to update the lawful-basis tests for processing personal data, to introduce the Smart Data scheme that the Energy Smart Data and Privacy Framework operates inside, and to update the rights of data subjects in respect of automated decision-making.

The Smart Data scheme matters for the energy data layer because it is the legal substrate for consumer-authorised data sharing. A consumer who wants a price-comparison service to read the consumer's half-hourly data, evaluate alternative tariffs and act on the consumer's behalf needs a legal route for the data to flow from the supplier or the DCC to the price-comparison service. The Smart Data scheme provides that route; the Energy Smart Data and Privacy Framework defines how it operates in the energy domain specifically.¹⁴

The second tier of governance is the Standard Licence Conditions. Each licensee (a generator, a transmission owner, a distribution network operator, a supplier) holds a licence granted by Ofgem under the Electricity Act 1989 and is bound by Standard Licence Conditions specific to its licence type. The conditions that govern the data layer include SLC 25 of the Electricity Distribution Licence which produces the Long Term Development Statement, SLC 11.5 which governs network charging methodology publication, SLC 49 which governs the publication of DNO data on connections, and the equivalent transmission licence conditions for the LTDS publication by the TOs.^{1 12} Each SLC is a child of the 1989 Act and can be amended by Ofgem through the standard licence-modification procedure (with a statutory consultation, an Authority decision and a right of appeal to the Competition and Markets Authority).

The third tier is the industry codes. The Balancing and Settlement Code, the Connection and Use of System Code, the Distribution Code, the Grid Code, the Master Registration Agreement, the Retail Energy Code, the Smart Energy Code and the Uniform Network Code together cover every operational data flow in the system. Each code is owned by a code manager (Elexon for the BSC, NESO for the CUSC, the Distribution Code Review Panel for the Distribution Code, NESO for the Grid Code, the MRA Service Company for the MRA, the Retail Energy Code Company for the REC, Smart DCC for the SEC, and the Uniform Network Code committees for the UNC). Each code has a modification procedure (a CMP for the CUSC, a P for the BSC, a GC for the Grid Code, an SEC modification for the SEC) and a code panel that decides on raised modifications under the procedure.

The fourth tier is the data-specific licence conditions. The LTDS Direction of 30 April 2024 is the most recent example: Ofgem issued the Direction under SLC 25.2 of the Electricity Distribution Licence requiring the move from Excel files to a validated CIM data model, with phased delivery across Stages 1, 2 and 3.¹ The third derogation letter of 13 May 2026 reshaped Stage 2 contents while holding the publication date.² Each new data publication obligation that lands on a licensee follows this pattern: a Direction or a licence amendment names the artefact, the format, the cadence and the validation requirement; the licensee publishes; Ofgem holds the publication to the requirement.

The fifth tier is the consumer-facing rules. The Energy Ombudsman handles consumer complaints; the Citizens Advice consumer service handles consumer advice and signposts to the Ombudsman; the Public Sector Equality Duty under the Equality Act 2010 binds Ofgem and DESNZ in their consumer-facing decisions; the Vulnerability Strategy under SLC 0 of the Electricity Supply Licence requires the supplier to identify vulnerable consumers and apply specific treatment to them. The fuel-poverty statistics published by DESNZ define the population that the consumer-facing rules treat as vulnerable; 11.0 percent of English households (2.7 million homes on the LILEE metric) were in fuel poverty in the latest official statistics, and the Warm Homes Plan funds energy-efficiency measures for 5 million homes.

The sub-page treats each tier with the named instruments, the procedure for amending each instrument and the consultation routes that a reader can engage with when an amendment is in flight. The May 2026 priority list for the sub-page is the post-DUA Act updates to UK GDPR, the operationalisation of the Energy Smart Data and Privacy Framework and the in-flight code modifications that affect the data layer.

Sub-page anchors: Rules, Governance, Privacy. The three pages are at first-draft quality and queued for a follow-up rewrite to merge them into a single gold-standard rules-and-governance page per the master plan §E.4.

Sub-domain 5: Planning data and the future-scenarios stack, from FES to SSEP to CSNP

The planning-and-future sub-domain covers the data flows that feed strategic planning. Strategic planning in GB has been reshaped by the summer 2025 REMA Phase 2 decision and the spring 2026 CSNP methodology approval; the data layer behind it is now the centre of gravity for system-wide projection work for the rest of the decade.

The Future Energy Scenarios are the long-running NESO scenarios that describe four possible system futures (Holistic Transition, Hydrogen Evolution, Electric Engagement and Falling Short in the most recent edition; the names evolve between editions). FES has been the canonical projection stack since 2011 and updates annually each July. The FES dataset is published under the NESO Open Licence and is the reference projection set for almost every market-facing analysis in GB.

The Strategic Spatial Energy Plan replaces FES as the centrepiece strategic-planning artefact under the post-REMA architecture. NESO is developing SSEP with DESNZ; the methodology was published in May 2025, the first SSEP iteration is due in Q4 2026, the public consultation runs in early 2027 and the final SSEP is due in Autumn 2027.¹⁰ The SSEP is the spatial counterpart to FES: where FES describes the total system at the national level, SSEP describes where assets should sit at the spatial level (which transmission node a wind farm should connect to, which DNO area a battery should sit in, which region a hydrogen production cluster should serve).

The Centralised Strategic Network Plan is the network-investment counterpart to SSEP. NESO is developing CSNP with Ofgem; the methodology was approved by Ofgem in April 2026, the transitional T-CSNP is due in June 2026 and the first full CSNP delivery is due by the end of 2028.^{15 11} The CSNP replaces the Network Options Assessment as the canonical network-investment plan; it sets out the network reinforcements needed to deliver the assets that SSEP places, and it sets the investment envelope that Ofgem then approves through the price-control framework.

The data flows behind SSEP and CSNP come from GC0139. The Grid Code change GC0139 was a workgroup proposal that progressed to a workgroup report in December 2025; the change updates the Grid Code to mandate the network licensees to publish the planning data that SSEP and CSNP consume, in a format that NESO can ingest at the SSEP and CSNP cadence.³ Without GC0139, NESO would have to negotiate bilateral data-sharing agreements with each of the three TOs and each of the six DNO groups for each SSEP and CSNP iteration; with GC0139 in place the data publication becomes a licence obligation under the Grid Code.

The planning-and-future sub-domain also covers the Distribution Future Energy Scenarios that each DNO publishes. The DFES are the DNO-area equivalents of FES; each DFES describes the projected demand and embedded generation at each substation in the DNO's area under four scenarios. The DFES feed the Embedded Capacity Register and the DNO's own Network Development Plan.

The data-volume picture in this sub-domain is smaller than the operational sub-domains (lifecycle, physical data generation) but the data-format picture is more demanding. SSEP and CSNP need consistent regional, substation-level and asset-level data across every DNO and TO; the data-format work behind GC0139 is the work that makes that consistency possible. The LTDS move to CIM (covered in sub-domain 6) is part of the same picture: without a shared data model the planning artefacts cannot reconcile their inputs across licensees.

The sub-page also tracks the timetable. T-CSNP is due in June 2026; SSEP Q4 2026; CSNP end-2028; FES annually each July. A reader who arrives wanting to know when the next strategic-planning artefact lands and which dataset they should be reading at the time uses this sub-page as the cadence reference.

Sub-page anchors: Planning data, Future scenarios. The two pages are at first-draft quality and queued for a follow-up rewrite to merge them into a single gold-standard planning-and-future page per the master plan §E.4.

Sub-domain 6: CIM and interoperability under the BSI engagement portal

The CIM-and-interoperability sub-domain covers the data-model substrate that all five other sub-domains share. The Common Information Model is the family of IEC standards that defines a shared data model for the electricity system: IEC 61970 (the EMS-API base), IEC 61968 (the distribution-management interfaces), and the ENTSO-E Common Grid Model Exchange Standard (CGMES) profiles that adapt the IEC base for cross-border model exchange in Europe. GB has adopted CGMES 3.0 plus the IEC 61968-13 distribution profiles for the LTDS, which makes the LTDS the first major GB instance of a CIM-formatted public data publication on a regulator-set cadence.

The IEC base standards are: IEC 61970-301 Edition 7.0 with Amendment 1:2022, the Common Information Model base for energy-management-system application program interfaces; and IEC 61968-13 Edition 2.0 (BS EN IEC 61968-13:2021), the Common Distribution Power System Model profiles for distribution-network exchange.^{6 7} The two standards together describe the topology and the asset attributes of an electricity system at the level of detail needed for operational and planning analysis. ENTSO-E published the CGMES 3.0 base in 2021 and the Application Profiles Library version 1.1.1 patch in October 2025, with the NC (network code) profile releases continuing through March 2026.⁵

The BSI engagement portal at https://cim.bsigroup.com/ is the GB engagement route for the CIM standards.⁴ The portal runs the GB feedback loop into the IEC and ENTSO-E standardisation processes, and hosts the working group activity that produces the GB-specific profile extensions. The portal is the canonical place a GB analyst, modeller or licensee engages with the CIM work; a sub-page reader looking for the current state of any profile starts at the portal.

The CIM workstream has four layers in GB. The first layer is the base IEC standards. The second layer is the CGMES profiles that ENTSO-E publishes on top of the base; CGMES 3.0 is the version GB has adopted, with the Application Profiles Library v1.1.1 patch from October 2025 as the most recent revision.⁵ The third layer is the GB-specific extensions. GB adds a small set of extensions to the CGMES profiles where the GB regime requires asset attributes that are not in the standard profile (for example, asset attributes specific to the GB licence categorisation, or to the GB connection-stage process). The fourth layer is the validation. CIM publications are validated against SHACL shapes that the BSI portal hosts; SHACL is the W3C Shapes Constraint Language that validates RDF data against a schema. An LTDS Stage 2 publication that fails the SHACL validation is not a compliant publication.

The mRIDs are the master resource identifiers that tie each topology element to a stable identifier across publication cycles. An mRID is a UUID assigned to each topology element (a substation, a transformer, a line section, a connection point) at the first publication and retained across every subsequent publication that includes that element. The mRID lets a reader compare two Stage 2 publications from successive years and identify which elements have been added, removed or modified; without stable mRIDs, the comparison would require structural matching across the topology and would be fragile to renaming.

The first GB instance of a CIM-formatted public data publication is the LTDS Stage 2 publication of 29 May 2026 under the third Ofgem derogation letter.^{1 2} Stage 2 covers the topology and the asset-attribute data for each DNO area; Stage 3 (due 30 November 2026) adds the planning data and the connection-stage data. The two stages together describe each DNO area in a format that any planning team can read against without bespoke parsing of Excel files.

The interoperability picture for this sub-domain is the interoperability across the five other sub-domains. The actors-and-roles sub-domain identifies the actors that produce and consume CIM-formatted data; the physical-data-generation sub-domain covers the meters and telemetry that feed into the CIM-formatted asset register; the lifecycle-and-settlement sub-domain depends on the asset register to compute the network charges that flow into the settlement; the rules-and-governance sub-domain covers the licence conditions and the Directions that mandate CIM-formatted publication; the planning-and-future sub-domain reads the CIM-formatted LTDS as one of the input datasets to SSEP and CSNP. The CIM substrate is the data-model layer that makes the other five sub-domains interoperable rather than siloed.

The May 2026 priority for this sub-domain is the LTDS Stage 2 publication itself and the SHACL validation against the Stage 2 contents. The sub-page treats every layer of the CIM stack with worked examples and links to the BSI portal where the active engagement happens.⁴ Cross-links to LTDS explained open the LTDS-specific treatment of how mRIDs resolve, how SHACL validates a CIM profile and how each Stage 2 publication is structured.

Sub-page anchor: CIM and the related Digitalisation Framework page. Both sub-pages are at first-draft quality and queued for a follow-up rewrite to consolidate them into a single gold-standard cim-and-interoperability page per the master plan §E.4.