XWärmeplan: data standard for municipal heat planning in Germany

Why a data standard for heat plans?

Under the German Heat Planning Act (WPG), cities and municipalities are required to draw up heat plans. In practice, these plans are still mostly produced as a PDF report with a map annex. The underlying geodata comes in widely varying formats and structures, depending on which consultancy was commissioned and which software was used.

This creates three practical problems:

• Updating: Heat plans have to be revised regularly. Without structured data, revision is effectively tied to the consultancy that produced the original plan.
• Reuse: Other types of planning, such as urban land-use planning under the German Building Code (BauGB), cannot readily adopt the results.
• Comparability: Heat plans from different municipalities cannot be aggregated or analyzed across regions.

A uniform, machine-readable data format addresses exactly these points. For urban land-use planning, such a format has existed for years in the shape of XPlanung. XWärmeplan applies the same principle to heat planning.

What is XWärmeplan?

XWärmeplan is a domain schema developed by the XLeitstelle Planen und Bauen, the central coordination office for the XPlanung and XBau standards. It builds on the established XPlanung standard and defines how the result data of a municipal heat plan is structured, georeferenced and made machine-readable.

Technically, XPlanung is an open, XML-based exchange format based on Geography Markup Language (GML). A heat plan following XWärmeplan is therefore exchanged as an XPlanGML file, just like a local development plan.

The data model is object-oriented. The central class WP_Plan represents a heat plan pursuant to Section 23 WPG and covers, among other things, the cartographic representation of the status-quo and potential analysis, the division into heat supply areas, the indicators of the target scenario, the supply technologies for the target year, and the measures of the implementation strategy. Below that sit domain-specific object types, for example WP_WaermeverbrauchLinie for linear heat density per street segment. Textual and graphical explanations can be attached as external references.

Key terms at a glance

Exchange formats and tools

The XWärmeplan specification is generated in a model-driven way from a conceptual UML model. This produces not only the XML schema and the object type catalog, but also further representations of the same data model. For practitioners, the key consequence is this: XPlanGML is not the only exchange format. Alongside the classic GML encoding, a JSON-FG representation is provided as well. JSON-FG is an OGC format for features and geometries that avoids the limitations of GeoJSON regarding coordinate reference systems and feature typing.

Initial tools are already available, generally as open source:

• XPlan-Tools, a Python library that converts, validates and migrates XPlanung, XTrasse and XWärmeplan data between GML, JSON-FG and database encodings. PostgreSQL/PostGIS, GeoPackage and SpatiaLite are supported.
• The XMAS plugin for QGIS, which can create plans from scratch, import and edit existing GML files, and export as GML or JSON-FG. It builds on XPlan-Tools and a Postgres database.
• ldproxy, a server that publishes the data as OGC API Features. This allows heat planning data to be consumed as a geospatial service rather than passed around as files.

Current status

The object type catalog for the heat plan domain schema is published on the XLeitstelle website and can be inspected there. However, there is currently no obligation to use it. The XLeitstelle proposal is being discussed in working groups of the German IT Planning Council; organizational responsibility for XWärmeplan remains with the XLeitstelle, from where it is to be submitted to the IT Planning Council.

The standard is already referenced in the ongoing parliamentary process for the WPG amendment. The provision is that data must be submitted in a format specified for the data space, and that the format to be used will be announced on the data space website. Binding force is therefore likely to follow not directly from the act itself, but from the requirements of the data space.

What this means for consultancies and municipalities

For municipalities, procurement is the most relevant angle. Requiring delivery of the result data in the XWärmeplan schema in the tender documents today reduces dependency on the commissioned consultancy and makes both later revisions and submission to the data space easier.

For consultancies and engineering offices, the question is one of tool chains. Results that already exist as geodata, such as heat supply areas, linear heat densities or potential areas, can be transferred into the schema with reasonable effort. We have described elsewhere which building data is available for heat planning and which tools are used in municipal heat planning. Partially vectorized capture of existing, not fully digitized heat plans is also possible, so that a structured data basis can be built up step by step.

XWärmeplan and detailed planning with nPro

Municipal heat planning provides the strategic layer: where does a heat network make sense in principle, and where is decentralized supply the better option? The actual design of a network only comes afterwards. This is exactly where nPro comes in, with the sizing of heat networks, the design of the energy hub, and the economic assessment of supply variants.

The data from a heat plan is a good starting point for this. Delineated heat supply areas define the study area, heat demands per building or street segment provide first indications for load profiles, and designated potential areas point to possible generation sites. The more structured this data is, the more directly it can be carried over into detailed network planning.

You can already import and process your own geodata in nPro today. See GIS data upload and GIS exports for how this works.

If no heat plan is available yet, or if its data is not building-specific, the necessary basis can be obtained through nPro directly. The building atlas provides building-specific data for all of Germany, from which heat demands and load profiles for a district can be derived. The potential analysis module supports the assessment of local generation potentials, as required for feasibility studies under the German BEW funding program, for example.

If you would like to use the results of a municipal heat plan as the basis for network planning in nPro, please get in touch.

Further information

External sources

• XPlanung at the XLeitstelle Planen und Bauen, including specifications and releases
• Object type catalog of the heat plan domain schema
• FAQ on the Heat Planning Act published by the German Federal Ministry for Economic Affairs and Energy
• FAQ of the Competence Center for Municipal Heat Transition (KWW), including model specifications for tendering
• XPlan-Tools, a Python library for converting and validating XWärmeplan data

Related pages on nPro

• Tools for municipal heat planning
• Building atlas: building-specific data for Germany
• Potential analysis
• Building data for heat planning
• Linear heat density
• Economic feasibility
• Transformation plan