Foundations stage summary

Energy system data means any data relating to the energy system, whether produced by, for, or about the energy system. That is Ofgem's definition, adopted in its decision on the Data Best Practice Guidance on 8 October 2024, and the wording matters because it replaced a narrower test that covered only data necessary for the operation of the system. The broadened definition pulls planning forecasts, asset registers, consumer consent records and innovation datasets into the scope of the guidance, so datasets that once sat outside the rules are now inside them.

The scale is worth holding in numbers. At the end of March 2026, 72 percent of all meters operated in smart or advanced mode, on DESNZ Q1 2026 statistics, with more than 41 million smart and advanced meters installed. Elexon expects MHHS processing to handle up to 500 billion half-hourly meter readings a year from May 2027. Thousands of SCADA-monitored substations are sampled every 2 to 10 seconds, producing around 69 million data points an hour for a large DNO, and about 20 gas chromatographs at National Transmission System entry points continuously measure the calorific value that prices every gas bill in GB.

The stage's reading frame is five unresolved tensions: open data against security risk, centralisation against fragmentation, consumer consent against system need, innovation speed against regulatory pace, and national standards against local variation. None of them has a clean answer. Every decision in energy data trades one legitimate goal against another, which is why the course keeps returning to who decides, under what instrument, rather than to any single right answer.

More than 40 organisations run the GB energy data estate, and they sort into six groups: government and regulators (DESNZ and Ofgem), system operation (NESO, publicly owned since 1 October 2024 under Energy Act 2023 powers), networks (three electricity transmission owners, six DNO groups, four gas distribution networks and National Gas), the code bodies (Elexon, RECCo, DCC and ElectraLink), industry bodies, and market participants. Each group produces, consumes or governs a distinct slice of the estate.

Data custody follows the institutions. NESO holds system data, the Future Energy Scenarios, the Data Portal and coordination of the Data Sharing Infrastructure. Elexon runs the BSC, settlement, the Insights Solution, the flexibility market facilitator role and the Smart Data Repository arriving in autumn 2026. The DCC operates the smart meter WAN and the Central Switching Service. RECCo governs the Retail Energy Code, the enquiry services and the Consumer Consent Solution. Xoserve is the gas central data services provider, running UK Link and Gemini, and the DNOs publish the LTDS, DFES, the Embedded Capacity Register and capacity heatmaps.

The everyday consequence is that a data request is routed, not searched. Whoever operates the register you need also answers to a specific code: the CSS is operated by the DCC but governed under the REC, settlement data flows under the BSC, and gas retail data lives under the UNC. One dated fact belongs in this map: the Gas and Electricity Enquiry Services replaced the older Data Enquiry Service on 18 July 2022, so pointing anyone at the DES today is pointing them at a retired service.

Every record in the market is keyed by a small set of identifiers. The electricity MPAN's 21 digits encode settlement treatment, not just identity: the top line carries the profile class, meter time-switch code and line loss factor class, and the core carries the distributor id, the unique number and a check digit. The gas MPRN does the same job for the other fuel, and MPXN is the collective term. Reading an identifier is therefore reading a set of market decisions about how that meter point settles.

Import and export are separate meter points, not signs on one number. A solar home holds an import MPAN and a separate export MPAN, each with its own register, which is why an import register never runs backwards. And the physical network must be kept distinct from its settlement geography: about 350 physical grid supply points roll up into just 14 GSP Groups, and it is the Groups that settlement and most regional data products use. Mixing the two up is how central settlement services get wrongly described as regional ones.

The registers hold the market's memory. The Central Switching Service has been the registration source of truth for both fuels since July 2022, with the Retail Energy Location record carrying the address; UK Link is the gas-side backbone; and profile classes with their standard settlement configurations are legacy structures now dying under MHHS. Identifier quality is a market-wide cost, because a wrong address or a mislinked meter point fails switches and pollutes settlement downstream.

The electricity system is a voltage cascade, and each tier produces its own category of data: generation connects at 11 to 25 kV, the 400 and 275 kV supergrid moves bulk power, grid and primary substations step down through 132 and 33 kV, high-voltage distribution runs at 11 kV, and the low-voltage network delivers 400 and 230 V to premises where the smart meter sits. Gas mirrors this with the National Transmission System and the local distribution zones, and gas billing is a two-input measurement: metered volume priced by continuously measured calorific value.

The telemetry lives in four main places: transmission SCADA, distribution monitoring, boundary metering at the grid supply points, and NTS and LDZ telemetry on the gas side. These feeds are operational technology data, carried on networks physically separated from the internet, and they are exactly the datasets where the open-data presumption meets its security limit.

The changing grid is why this module matters beyond background. Electric vehicles, heat pumps and rooftop solar all connect at the low-voltage edge, the layer the DNOs historically monitored least, so the fastest-growing operational question sits where the historic data is thinnest. That gap explains much of what stages 2 and 3 cover: half-hourly settlement, flexibility registers, and the monitoring and estimation products that stand in where meters do not exist.

The course groups the estate into 13 categories covering 87 distinct data types, each with a defined producer, consumer, governing instrument and sensitivity classification. The attribution matters: this is the course's teaching map, not an industry standard, and quoting it as an external authority is one of the stage's named pitfalls. Its value is practical rather than official, because it turns the shapeless phrase energy data into a set of types you can route.

Sensitivity does the legal work. The five-rung ladder runs from open data to restricted, and the personal against operational distinction carries most of the weight: half-hourly consumption data is personal data when it can be linked to an identifiable household, because it can reveal routines and occupancy, while SCADA telemetry is operational data whose risk is national security rather than privacy. Ofgem's Data Best Practice Guidance presumes openness, and the sensitivity classification is what a holder must argue from when it withholds.

The taxonomy earns its keep only when it routes real decisions. Worked end to end, a half-hourly import reading and a DFES scenario workbook land in different categories, on different rungs, with different producers, consumers and governing instruments, which is the whole point: two datasets that both count as energy system data obey entirely different rules. Profile classes appear in the taxonomy flagged as legacy, because MHHS replaces profiling with actual half-hourly data.

The smart metering estate is the largest single data instrument in GB, and its generations still matter. SMETS1 meters, installed first and initially tied to individual suppliers, went through a national enrolment: about 15 million were in the programme's eligible scope and just over 11.1 million had migrated onto the shared DCC network by May 2026. SMETS2 meters are DCC-native from installation. Inside the home, the HAN links meter, in-home display and comms hub; the WAN carries data from the comms hub to the DCC.

The WAN is not one technology. The North region uses Arqiva long-range radio and covers Scotland and northern England only. The Central and South regions run on Telefonica and Virgin Media O2 cellular, and they include all of Wales. The estate is also mid-transition: 4G comms hubs for the North were agreed on 30 May 2025, the DCC's current licence expires in September 2027, Ofgem's decision on the successor licence came in April 2026, and the business transfer is expected in November 2026, so DCC2 is a data continuity question, not a distant procurement.

What the meter records is equally precise. Import and export are separate registers against separate MPANs, so an import register never goes negative, whatever the midday sun is doing. And reads come in families under the DUIS specification: service request 4.1.1 reads instantaneous import registers on demand, while scheduled half-hourly profile reads for billing use the 4.8 family. Matching the read type to the use case is the difference between a snapshot and a settlement-grade series.