Municipal heat planning: getting started with a sustainable heat supply

Heat plans: legal basis in Germany 
The binding legal basis for comprehensive municipal heat planning as a future nationwide standard is the Wärmeplanungsgesetz (Heat Planning Act), which contains, among other things, content requirements and regulates the implementation of individual work steps. It is closely interlinked with the second amendment to the Gebäudeenergiegesetz,GEG (Building Energy Act). Both laws are based on the goal of achieving climate neutrality in Germany by 2045 and came into force on 1 January 2024. The Wärmeplanungsgesetz is supported by amendments to the Building Code and an adapted environmental impact assessment. 

The website of the Bundesministerium für Wohnen, Stadtentwicklung und Bauwesen (BMWSB) states, among other things: „The Wärmeplanungsgesetz creates the legal basis for the binding and systematic introduction of nationwide heat planning throughout Germany. As a pioneering instrument based on local conditions, heat planning is intended to show a way in which the heat supply can be gradually converted to the use of renewable energies or unavoidable waste heat in the future. The Wärmeplanungsgesetz contains specifications for content and a sensible sequence of individual work steps up to the creation of a heat plan, as well as staggered requirements for heat network operators to decarbonise their networks.“ 

What does this mean in concrete terms for local heat planning stakeholders?  
When drawing up local heating plans with public participation, the focus of the body responsible for planning (usually the local authority) is on a secure and cost-efficient, centralised or pipeline-based supply of sustainable heat, which must be free of fossil fuels in the long term (by 2045). Locally utilisable waste heat and renewable energies - such as solar or geothermal energy, biomass or from wastewater - play an important role in this. If network operators are planning to convert their gas networks to (green) hydrogen, this can also be considered as a heating option.

In all other municipalities that are still in the planning phase or have not yet started, patience is still required. Different deadlines apply for the completion of the heating plans: In municipal areas with more than 100,000 inhabitants, they must be completed by 30 June 2026. Municipalities with a smaller population, on the other hand, have two years longer.  

The so-called "convoy procedure" also offers smaller municipalities with fewer than 10,000 inhabitants the opportunity to develop a joint heating plan in an inter-municipal merger. In a simplified procedure, lower requirements also apply. 

2. Phases of municipal heat planning

The Wärmeplanungsgesetz provides for several steps in the complex municipal heat planning process. A large amount of data must be used and analysed. According to the BMWSB, „only existing data is used, which is primarily collected from publicly accessible registers and databases and from market players in the energy industry.“ 

Suitability test and abbreviated heat planning 
In a first step, an area is examined for sub-areas that are assumed to be unsuitable for centralised supply via a heating or hydrogen network. In the subsequent heat plan, the respective area is documented as a „prospective area for decentralised heat supply“, which means that abbreviated heat planning can be carried out for this area. 

Inventory analysis  
The inventory analysis determines the current local heat demand and consumption, taking into account the resulting CO2 emissions as well as all building and settlement types and building age classes. In addition, data on the entire supply infrastructure, consisting of gas and heating networks, heating centres and storage facilities, etc., is recorded. 

Potential analysis 
In this planning phase, utilisation and savings potentials are determined. Are there locally usable sources of renewable energy (solar or wind energy, geothermal energy, biomass, green hydrogen) or waste heat, e.g. from data centres or industrial plants? Are cross-sector energy savings possible (space heating, hot water and process heat)? 

Target scenario 2045 and implementation strategy 
Based on the available analysis results, a time-phased target scenario is developed below, which is intended to ensure the long-term coverage of the climate-neutral heating requirements of the respective municipality. To this end, suitable areas for heating networks (centralised supply) and for individual supply (decentralised supply) are identified. The scenario includes a detailed spatial depiction („heat supply areas“) of the supply structure in 2045, taking economic viability into account. Milestones are specified for the years 2030, 2035 and 2040. 

In the further course of planning, concrete measures and the appropriate type of heat supply for specific sub-areas will be developed and the responsibilities of municipal and local stakeholders will be specified.

3 Germany and the EU: heat planning in practice 

Germany: examples from the federal states  
In some German federal states, heat planning was already mandatory before 1 January of this year: 

Lower Saxony 
According to the Lower Saxony Climate Act, this federal state has been in existence since summer 2022 (Section 20 NKlimaG), 95 municipalities in the state have been obliged to carry out municipal heat planning by the end of 2026. The aim is to achieve a climate-neutral heat supply for buildings by 2040 - five years earlier than stipulated in the federal Wärmeplanungsgesetz. 

Baden-Württemberg 
Baden-Württemberg plays a pioneering role in municipal heating planning throughout Germany: the urban districts and large district towns there already had to submit their heating plans by 31 December 2023, according to which heating planning is currently available for around half of the state's inhabitants. 

• District of Lörrach: lighthouse project for inter-municipal heat planning  
  The district of Lörrach is regarded as a role model for an inter-municipal planning process (convoy). Within a period of 20 months, the potential for climate-neutral heat supply - such as geothermal energy, solar thermal energy, biomass or waste heat from industry and commerce - was recorded in 35 municipalities with a total of 300,000 inhabitants. The detailed catalogue of measures adopted in June 2022 forms the basis for the implementation and updating of local heat planning in the form of municipality-specific options for action. 
• Kehl and Strasbourg: cross-border heating alliance 

The idea of using the waste heat from Badische Stahlwerke to heat the building sector in the border towns of Kehl and Strasbourg, a project that is considered unique in Europe, was followed in 2019 by two feasibility studies that underpinned the economic viability and technical feasibility of the project. The Franco-German heat transport company „Calorie Kehl-Strasbourg“, which will be founded in 2022, will drive forward the construction of the pipelines and be responsible for their operation. Construction work is set to begin this year. The heat pipeline is scheduled to go into operation in 2027. 

Schleswig-Holstein 
When the amendment to the Energiewende- und Klimaschutzgesetze EWKG (Energy Transition and Climate Protection Act) came into force in December 2021, Schleswig-Holstein also introduced a state-wide heat planning obligation for larger municipalities ahead of schedule. The plans for so-called medium-sized and regional centres must be submitted to the local Ministry of the Environment this year at the latest. Other municipalities with special classifications have until 2027 to draw up their heating plans. 

Regional heat suppliers in Kiel and Flensburg are currently planning large-scale seawater heat pumps to supply district heating based on the Danish model. The pioneer is the port of Esbjerg in south-west Denmark, where the world's largest seawater heat pump is currently being built and which is already one of the most important energy ports for Germany. 

Esbjerg also plays a prominent role as the starting point for the Hyperlink III cross-border hydrogen pipeline for green H2, which is currently under construction. The pipeline, which is around 200 kilometres long, is due to be operational in 2028 and will extend via the Schleswig-Holstein bridgehead to Hamburg, where it will be connected to the nationwide German hydrogen network. 

Looking to Europe: best practice 
Denmark can certainly be described as a pioneer in the heating transition. As early as the 1970s, the country focussed on the use of renewable energies during the oil crisis (oil price shock) and obliged its municipalities to draw up heating plans. With the creation of a huge district heating network, CO2 emissions were reduced by 65 % within a decade.  

Today, around 65 % of households in Denmark are heated with district heating. A third of the waste there is used to generate energy.

A joint project between Wien Energie and a Digital Reality data centre is considered forward-looking: a heat pump system recently installed by the energy provider in Vienna's Florisdorf district uses the waste heat from the data centre to supply heat to the neighbouring clinic via a direct connection pipe. In this way, between 50 and 70 % of the clinic's heating requirements can be covered and up to 4,000 tonnes of CO2 can be saved each year. 

4. Outlook

A fundamental building block for the decarbonisation of our energy systems is the conversion of the heat supply, which today is still predominantly based on fossil fuels with correspondingly high CO2 emissions. The aim is to achieve a nationwide, climate-neutral heat supply by 2045. The legislator set the decisive and binding legal framework for this in 2023 with the Heat Planning Act and the Building Energy Act. The expansion of grid-based local and district heating and the development of a hydrogen pipeline network will play a central role in this.