The preparation of transformation plans for the decarbonisation of existing heat networks is funded under the Federal Support for Efficient Heat Networks (BEW). In this article you will learn more about the content of transformation plans.

What is a transformation plan?

The new construction of heating grids with high shares of renewable energies and also the decarbonisation of existing heating grids is promoted within the framework of the Federal Promotion for Efficient Heating Grids (BEW). A transformation plan shows how a heating network can achieve greenhouse gas neutrality by 2045 at the latest. To this end, the ACTUAL state, the GHG-neutral TARGET state in 2045 and the milestones to get there must be worked out. The BEW funding distinguishes between transformation plans and feasibility studies: transformation plans are prepared for existing heating networks, whereas feasibility studies are carried out for new heating networks.

Difference between a transformation plan and a feasibility study

In the BAFA's information sheet, the terms "feasibility study" and "transformation plan" are distinguished and defined: The feasibility study represents a document that assesses the fundamental economic and technical feasibility

of new heating networks to be built (feasibility study), or
of a greenhouse gas neutral target image of existing heating networks (transformation plan)

and outlines a path to greenhouse gas neutrality of the heating network by 2045. This already includes preliminary considerations as well as the determination of basic principles based on service phase 1 of the HOAI (Fee Structure for Architects and Engineers). A feasibility study therefore relates to a new heating network to be built, whereas the transformation plan relates to the target image of an existing heating network.

New construction of a heating network or transformation of an existing heating network?

The distinction between new construction and transformation is also defined in the BEW leaflets: New construction of a heat network is here either the initial construction of a heat network or the expansion of an existing heat network. The expansion of an existing network is only considered a new construction network if no more than 20% of the heat feed-in quantity of the part of the heating network to be expanded is provided from the existing network. The transformation of a heating network, on the other hand, is the conversion or extension of an existing heating network. An extension is only a heat network transformation if more than 20% of the total heat input quantity of the part to be extended is provided from the existing heat network. The planning and calculations must refer to the complete heat network in the case of transformation plans.

Which heat generators are subsidised?

The following heat generation technologies are considered eligible:

Solar thermal,
heat pumps for the use of environmental heat (air, surface water, waste water, near-surface geothermal energy, deep geothermal energy, waste heat, PVT collectors),
deep geothermal energy (if used only for heat supply),
solid biomass (restrictions apply), and
integration of waste heat.

Ineligible installations are recognised as biomass or renewable energy if only biomethane (on balance), biogas, sewage gas or landfill gas is used.

Which installations are not eligible?

Installations for the combustion of green hydrogen and synthetic fuels are in principle not eligible. Installations for the direct electric generation of heat from electricity (e.g. electric heating rods or electrode boilers) are not eligible (unless 100% of the electricity used comes from renewable sources, in which case certificates are not recognised).

When is a heating network considered to be greenhouse gas neutral?

A heating network is considered to be greenhouse gas neutral if the entire heat input into the heating network comes from eligible heat generation plants (or from CHP or boiler plants fired with renewable energies). A simple switch to hydrogen or synthetic fuels is therefore not considered greenhouse gas neutral. When using hydrogen or synthetic fuels, a switch of up to a maximum of 50% of the heat feed-in quantity is permissible. It should be noted here that plants for the combustion of green hydrogen and synthetic fuels are not eligible.

Eligibility criteria for the application

The following criteria will be used when applying for a feasibility study or transformation plan:

Share of renewable energies (incl. waste heat),
Target of greenhouse gas neutrality by 2045,
maximum biomass share (depending on grid size),
Minimum size of the network,
maximum temperature level,
maximum proportion of fossil-fired boilers, and
the depth of investigation/planning already in place.

The criteria are as follows:
Greenhouse gas neutral target scenario by 2045: As part of a feasibility study or transformation plan, a pathway must be described as to how the heating network will achieve greenhouse gas neutrality by 2045. Here, not only the target scenario must be outlined, but also the three intermediate steps in the years 2030, 2035, and 2040.
Maximum biomass share: Certain maximum biomass shares may not be exceeded in the heating network. For small heating grids (up to 20 km) this can be 100%. For medium-sized grids (20-50 km) this can be a maximum of 25% (towards the 2045 target), and for large grids (over 50 km) a maximum of 15%.
Minimum size: The network must supply at least 17 buildings or 101 residential units.
Maximum temperature level: For new heat networks (feasibility study), the maximum temperature level must not exceed 95°C in the flow at any time. In the case of existing networks (transformation plan), a temperature level above 95°C must be justified separately in the 2045 target picture.
Maximum share of fossil-fired plants: For new grids (feasibility study): The share of gas- or oil-fired boiler plants must not exceed 10%. Including CHP plants (combined electricity and heat generation), the maximum share of gas- and oil-fired plants in the heat quantity fed into the grid may not exceed 25%. For both new heat networks (feasibility study) and existing heat networks (transformation plan), it must be set out how the proportion of fossil-fuelled boiler and CHP plants is to be completely replaced by 2045.
Existing depth of investigation/planning: Initial quantitative preliminary investigations and conceptual designs must already be available at the time of application.

With the nPro tool, many steps in the preparation of a feasibility study can be completed in a short time.

What must a feasibility study or transformation plan include?

The level of detail of a feasibility study (planning of a new heating network) is comparable to service phase 1 of the HOAI. The following minimum contents are to be worked on here:

1.) ACTUAL analysis of the study area

Central to the ACTUAL analysis is the determination of the heat demand of the buildings that are to be connected. New buildings, existing buildings, commercial units and industrial companies must be taken into account. The information sheet on the BEW Act provides for a tabular form with the following data:

Type of end customers to be supplied (residential, industrial, ...)
Number of end customers to be supplied
Number of buildings and residential units
Number and technical key figures of the transfer stations
Heat demand of the respective end customers
Temperature level of the respective end customer
Current type of heat supply to the end customer

For transformation plans, the type of connection (new or existing) and the type of building must also be indicated. Furthermore, a spatial representation of the study area must be provided. In the case of the expansion of a heating network (feasibility study), data on the existing heating network must also be provided. The same applies to transformation studies, where an ACTUAL analysis of the heat network must be carried out. This must include the following parameters:

Hydraulic operating description and pressure levels (utilisation, bottlenecks and reserves)
Temperature curves (flow and return)
Network type
Type of pipeline
Pipe dimensions
Pipe lengths (distribution lines and house connection lines)
Insulation standard
Number and size of heat storage tanks and their mode of operation
Number of heat generation systems
Energy source per heat generator
Output per heat generator
Heat input quantity per heat generator
Type of system per heat generator (e.g. CHP or boiler)
Heat source of the heat generator (especially with regard to heat pumps)

2.) Determination of the potential of renewable energies and waste heat

For the determination of potential, all renewable energies and waste heat sources listed in the application are to be discussed in more detail, especially with regard to their availability. The renewable heat sources are solar thermal energy, geothermal energy, environmental heat (e.g. air, geothermal collectors, geothermal probes, groundwater, river water, lake water, wastewater) and biomass. For solar thermal energy, for example, the availability of land must be examined (e.g. open spaces, roofs, landfills). This also includes the necessary discussions with landowners to clarify whether they are prepared in principle to make their land available. In the case of geothermal energy, the exploration risk is to be minimised in the course of geological and seismic investigations and a suitable drilling site for the plant is to be identified. In the case of environmental heat sources, the usability of the heat source shall be examined, in particular geological and hydrological conditions. A test borehole can be drilled for this purpose. If biomass is part of the heat supply, its availability has to be checked and the origin and logistical effort (transport and storage) have to be included in the analysis. For waste heat, the industrial or commercial process must be described in concrete terms, including the relevant technical parameters (heat quantity, temperature level, availability, dependence on production). The industrial process must also be evaluated from the point of view of internal process optimisation through efficiency measures. The necessary discussions with companies are to be conducted and documented.

3.) TARGET analysis of the heating network (incl. primary energy savings and CO2 savings)

In the TARGET analysis, the heat generators, transfer stations and technical parameters of the heating network are shown. The technical parameters include:

Network type
Type of pipeline
Pipe dimensions
Flow and return temperatures
Pressure ratios
Volume flows

A thermo-hydraulic simulation of the heating network can be carried out to determine this. In addition, the primary energy savings and CO2 savings are to be determined, based on a comparison between the ACTUAL and TARGET status. If only new buildings are concerned, a combination of gas condensing boiler (85%) and solar thermal system (15%) can be used for the ACTUAL state of the heat supply.

4.) TARGET analysis of the heating network (incl. primary energy savings and CO2 savings)

To determine the cost framework, profitability and financing concepts must be prepared. For this purpose, the investment sums of the individual components of the heating network as well as the operating and consumption-related costs are to be roughly determined. A profitability calculation of the heating network is to be presented and it is to be shown how the investments are to be financed. For this purpose, risk analyses and a cost specification are to be defined, among other things.

5.) Pathway to greenhouse gas neutrality

In this part, a timetable for the implementation of the TARGET analysis is described. The following parameters are to be presented in tabular form for the milestones 2030, 2035, 2040 and 2045.

Share of renewable energies excluding biomass for the respective milestone and explanation of the measures to be implemented for this purpose)
Share of biomass
Share of waste heat
Share of hydrogen-fired CHP plants
Share of hydrogen-fired boiler plants
Proportion of waste-fired and combined heat and power plants
Share of gas-fired CHP plants
Share of gas- and oil-fired boiler plants
Number of end customers
Number of buildings and residential units
Route length (network size) (in km)
Total heat demand (in GWh/a)
Temperature level (in °C for flow and return)

The heat quantities are to be stated in percent and GWh/year. In addition, the measures to be implemented to achieve this must be explained.

Software tools for the preparation of a feasibility study or a transformation plan

For the preparation of a feasibility study or a transformation plan, numerous geo-referenced technical data on the heating network and the connected buildings must be collected. GIS programs are suitable for managing large georeferenced data. A free, open-source program is QGIS. QGIS offers a variety of data interfaces and is excellent for data management. In order to digitally map a planned heat network or one that is to be transformed, special simulation software for heat networks can be used. The nPro software can be used to design heat supply solutions. It is suitable for the creation of load profiles, the rough heat network calculation as well as the determination of an optimal supply variant. The nPro tool can also be used to map the targets for the path to greenhouse gas neutrality.

How is a transformation plan funded through BAFA?

Within the framework of Module 1 (feasibility study/transformation plan), services that are based on the work phases 2-4 of the HOAI are eligible for funding. Within the framework of modules 2 and 3 of the funding guideline, however, services that are based on the service phases 5-8 of the HOAI are eligible for funding.

Transformation plan for district heating networks

The decarbonisation of district heating networks is a huge challenge for network operators. Especially in urban areas, there is a lack of space to develop alternative heat sources such as geothermal or solar thermal energy. Technical modifications to the network, such as the laying of larger pipe diameters, are also very cost-intensive (up to 10,000 €/m in inner cities). Since merely changing the energy carrier (e.g. from natural gas to hydrogen) is not expedient, grid operators must tap every available heat source, first and foremost waste heat sources and environmental heat sources such as rivers or sewage treatment plants.

How much does it cost to create a transformation plan?

The costs for creating a transformation plan vary greatly with the size of the network. They range from around €150,000 for small networks to several million euros for large district heating networks. However, due to the attractive funding conditions of the BEW, it is always a sensible investment for heating network operators and municipal utilities, as early planning of the transformation of their heating network avoids high follow-up costs.