Introduction The Capacity Heatmap data is a requirement defined in Form of Long Term Development Statement (LTDS) and is being published for the first time as part of this LTDS cycle. As described in Section 6 of the Form of LTDS, the data provides a standardised view of available network capacity, constraints, and recent connection activity across the distribution network. It supports users in understanding where demand and generation connections may be possible, where network constraints may exist, and how recent connection activity may influence future network planning and connection decisions. Further details on the Capacity Heatmap data structure and requirements are provided in LTDS Capacity Heatmaps Appendix 1 – Information Model. The latest version of the appendix is available through BSI GB CIM Engagement Hub. The heatmap data is structured around a HeatmapDataSet, which represents a single published dataset and contains publication metadata such as the dataset title, description, publisher, issue date, validity period, coverage, format, and rights information. Within the HeatmapDataSet, Substation records provide the main operational view of the network, including location, voltage levels, licence area, demand and generation capacities, available capacity, constraint indicators, limiting factors, and references to related network hierarchy points such as Grid Supply Points (GSPs) and Bulk Supply Points (BSPs). The dataset also includes ConnectionActivity for substations where connection activity has occurred during the past year. This element summarises the number and total capacity of budget estimates provided, connection offers made, and connection offers accepted for both demand and generation connections. It provides useful context for interpreting available capacity, as it shows recent customer activity that may affect future network utilisation and planning decisions. For more information please see the UK Power Networks guide to Capacity Heatmaps: UK Power Networks LTDS Capacity Heatmaps Methodological Approach The source data for this release is drawn from the 2026 LTDS publication together with UK Power Networks Network Scenario Headroom Reports and additional in-house data where required. To support consistency across published datasets, the longitude and latitude values used in the Capacity Heatmap data have been aligned with relevant location data available through the UK Power Networks Open Data Portal. For a detailed understanding of the data scope published in the May 2026 LTDS cycle, users should refer to the LTDS Stage 2 Publication Notes, which set out the specific content and limitations of the LTDS data. Quality Control Statement Quality control checks were undertaken during the development of the Capacity Heatmap data to support consistency, completeness, and accurate representation of the published information. The heatmap data was checked against the relevant source datasets, including the LTDS publication data, Network Scenario Headroom Report outputs, and supporting in-house data. These checks confirmed that the values included in the heatmap publication are consistent with the available source data and are reflected correctly in the published outputs. The JSON export was validated through an import and review process to confirm that the file structure, attribute values, and licence-area outputs could be read and analysed as expected. This provided an additional assurance check on the integrity and usability of the published JSON format. Assurance Statement The DSO Network Insights Team checked to ensure data accuracy and consistency. Other Download the full JSON files from the Attachments section on this dataset. Definitions of key terms related to this dataset can be found in the Open Data Portal Glossary: https://ukpowernetworks.opendatasoft.com/pages/glossary/To view this data please register and login.