The projects are expected to deliver on one of or combination of the following topic outcomes:

• Faster transition of district heating systems towards low-temperature operations
• Faster transition of building heating systems towards low-temperature operations
• Increased use of renewable energy and/or waste heat.

Low-temperature district heating systems in urban areas offer higher potential for integration of renewable energy sources and waste heat, but their deployment is slowed down because the existing stock of inefficient buildings has been designed for high-temperature heat delivery systems. The topic supports the creation of the conditions necessary for the conversion of existing supply solutions – district heating, as well as individual heating ones – into low-temperature alternatives, along with reducing and optimising the heat load of buildings.

Efficient district heating systems are expected to meet increasingly stringent criteria in terms of the use of renewable energy, waste heat and/or co-generation in line with Article 26(1) of the Directive (EU) 2023/1791. To help district heating operators meet those criteria, there is a need to demonstrate solutions that support the transition to low-temperature district heating systems operating at supply temperatures at below 70°C.

There is currently a limited choice of established non-fossil fuel heating and hot water systems to replace fossil-fuel based heating systems in multi-apartment buildings. There is a need to demonstrate systems based on heat pumps solutions to replace both central and individual fossil fuel boilers in existing residential multi-apartment buildings.

Proposals are expected to address at least two of the following:

• Demonstrate system design and technical solutions at district and building level, to enable the integration of various heat supply sources (particularly renewable energy sources and waste heat), and to facilitate the transition to low-temperature district heating systems. Furthermore, refine digital tools for the control and monitoring of district heating systems as well as digital tools to support decision-making both at the initial planning stages and for the standardized replication of solutions.
• Demonstrate building-level heating solutions for hot water and low-temperature heating with maximum heating supply temperatures up to 50°C and fulfilling water safety regulations in at least four residential multi-apartment buildings of at least 1000 m2 each. The solutions should be transferrable and standardised.
• Demonstrate building-level heating solutions for hot water and heating needs in at least four residential multi-apartment buildings of at least 1000 m2 each that use either on-site renewable energy sources or an ambient or geothermal loop shared with other buildings / facilities, or a connection to district heating systems for the heat supply.
• At a building, district or city level, demonstrate approaches for connecting buildings via district heating networks and ambient or geothermal loops to reduce the overall energy demand, to facilitate the deployment of low-temperature district heating systems and to improve heating systems’ flexibility via the integration of heat storage, including in heat networks, by or with the inclusion of energy communities.
• Ensure the participation of local energy communities to assess their socio-economic benefits for the local community and heating system operators.

Projects are expected to demonstrate the proposed solutions in two different climate zones, at building, district and/or city level, and to assess the environmental, social and economic benefits of the proposed solutions for the local community and heating system operators while accounting for the regional economic and regulatory aspects. The system design must include advanced controls to allow exploiting the energy flexibility of individual heating systems in a collective way. Projects must present a concise state-of-the-art of existing relevant solutions, knowledge and tools from EU funded projects.

Projects are expected to contribute to the implementation of Climate City Contracts and/or Sustainable Energy Action Plans, Sustainable Energy and Climate Action Plans. Collaboration with the Cities Mission Platform is essential. The collaboration with the Cities Mission Platform must be formalized through a Memorandum of Understanding to be concluded as soon as possible after the project starting date. Under the guidance of the Cities Mission Platform, the selected projects will engage in clustering activities with other relevant projects supported under the Cities Mission to promote synergies and complementarities. Proposals should ensure that appropriate provisions for activities and resources aimed at enforcing clustering activities and cooperation with the Cities Mission Platform are included in the work-plan.