How can the climate-friendly heating transition succeed in metropolises, cities, and municipalities worldwide – and do so in a safe and affordable way for millions of households and businesses? Are district heating networks the answer, and can they truly help phase out fossil fuels on a large scale?
Around the globe, experts from energy supply, municipal utilities, planning, and industry are searching for answers to these questions. More than that, they want to actively shape the transformation of district heating. The decarbonisation of district heating is one of the central challenges of the global energy transition. While the electricity sector has already made significant strides in integrating renewable energies internationally, the heating sector has so far lagged behind. In urban areas especially, where individual solutions such as heat pumps face structural and infrastructural limits, district heating is a crucial tool for achieving climate targets.
International initiatives such as the European Green Deal, the Energy Efficiency Directive and the Renewable Energy Directive set ambitious targets for the expansion and decarbonisation of heating networks. Cities and utilities around the world are therefore faced with the task of modernising existing networks, integrating new technologies, and overcoming regulatory and financial hurdles.
The decarbonisation of district heating is a central goal of international climate policy. This type of heat supply is seen worldwide as a key tool for reducing CO₂ emissions in the building sector and achieving the ambitious climate targets, such as climate neutrality by 2045.
The European Union, numerous national governments, and international organisations view district heating networks as a crucial technology for the heating transition. For example, as part of the "Fit for 55" package, the European Commission emphasises the need to switch district heating more to renewable sources and to modernise existing networks. The German government is also planning to supply around 14 million residential units with climate-neutral district heating by 2045, which will require a massive expansion and transformation of the networks.
In densely populated urban areas, where individual solutions such as heat pumps face structural and infrastructural limits, district heating enables the efficient, bundled supply of entire districts or cities. As such, it serves as a systemically important backbone for the urban energy transition.
The international community has agreed to gradually transition district heating to CO₂-neutral sources. National strategies, such as Sweden’s climate policy or Berlin’s heat transition, serve as examples: Sweden aims for climate neutrality by 2045, focusing on the modernisation and decarbonisation of district heating networks. In Berlin, the climate-neutral transformation of heating networks is a key instrument for drastically reducing emissions in the building sector.
The challenge remains to align ambitious political objectives with concrete investments, innovative technologies, and a comprehensive modernisation of infrastructure. District heating is therefore not only a technical issue but also a politically and socially relevant topic – and a decisive factor in the global energy transition.
What makes district heating so relevant today? And why is it at the centre of the urban energy transition? A look at current supply priorities, international grid densities, and CO₂ balances highlights how different the starting points are. At the same time, it is clear that district heating opens up new ways to achieve climate targets and use infrastructure efficiently, particularly in growing cities.
District heating networks are a crucial building block for the decarbonisation of heat supply worldwide. According to the IEA (International Energy Agency), around 350 million building units are expected to be connected to district heating networks by 2030 – especially in urban conurbations with high heat density. However, network density and coverage vary internationally.
For example, in Denmark, more than 60% of households are connected to district heating, whereas in Germany the share is around 15% – a figure that is even lower in many other countries. The CO₂ balance of district heating depends largely on the energy sources used: historically, fossil fuels such as coal and natural gas have dominated, but the share of renewable energies and industrial waste heat is steadily increasing.
| System Type |
Typical CO₂ emissions (g CO₂eq./kWh heat) |
Primary energy source(s) |
|
Classic district heating (coal) |
239–265 |
Coal, fossil fuels |
|
Classic district heating (natural gas) |
133–197 |
Natural gas, fossil fuels |
|
Modern CHP (CCGT, natural gas) |
151 |
Gas-fired CHP, high-efficiency |
|
Decarbonised district heating |
<60 |
Biomass, geothermal energy, waste heat |
As part of an extensive district heating and geothermal energy project in Waren an der Müritz, the aquatherm energy pipe system is currently being installed. In the future, the pre-insulated piping system will supply numerous buildings with cost-effective heat. Integrated leakage monitoring ensures the district heating pipeline is even safer, as the aggressive brine pumped from the earth's interior at around 70 °C must not come into contact with groundwater. Despite the salty water, this is impossible thanks to the corrosion-resistant polypropylene piping system.
Copenhagen operates the world’s largest district heating network and aims to make it almost climate-neutral in the near future. The conversion from coal to sustainable biomass, the use of large heat pumps, and the utilisation of waste heat and geothermal energy will save around 500,000 tonnes of CO₂ annually. Currently, 98% of all buildings are connected.
Since 2006, the Katri Vala Heating and Cooling Plant has been using large heat pumps that recover waste heat from wastewater. With a heating capacity of 126 MW, residential buildings are supplied with low-emission district heating, significantly improving the city’s CO₂ savings.
A new district heating system in the Txantrea district reduces CO₂ emissions by up to 80%. It supplies thousands of households sustainably and is part of the city’s urban strategy for climate neutrality.
The Lithuanian capital relies on the largest absorption heat pump in the Baltics, which uses industrial waste heat. This reduces dependence on gas and biomass while significantly increasing the efficiency of the district heating network.
Vaasa uses former oil deposits as seasonal heat storage for renewable energy. The project has reduced coal use in district heating by over 30% and increases security of supply.
Reykjavik is a pioneer of geothermal district heating. The Silverstone project at the Hellisheidi power plant will further develop it into one of the first almost CO₂-neutral geothermal plants in the world.
A solar thermal district heating system with seasonal heat storage has been established here. It covers a large part of local heating demand and substantially reduces CO₂ emissions.
By 2025, Aarhus will build Europe’s largest geothermal district heating plant. The project will decarbonise a significant part of the city’s heat supply and serve as a model for other major cities.
Modernisation of the district heating network with large-scale heat pumps and the integration of renewable energies makes Vienna one of Europe’s leading cities for sustainable heat supply.
The city uses district heating technology to provide low-carbon heat even at extreme sub-zero temperatures, reducing emissions and significantly improving air quality.
As urbanisation progresses, more than 68% of the world’s population is expected to live in cities by 2050, making efficient, centralised heat supply systems increasingly important. The way district heating works makes it possible to harness renewable energy, industrial waste heat, and innovative technologies in a bundled and efficient manner.
This reduces both the space requirements and the complexity of individual heating systems – a major advantage in densely built-up areas. It also supports the integration of cross-sector solutions, such as coupling electricity, heat, and mobility.
District heating systems consist of central heat generators, insulated pipeline networks, and transfer stations at the consumer’s end. The heat is transported as hot water or steam, with modern networks operating at lower temperatures to minimise losses and allow the integration of renewable sources.
The technology has evolved from the earliest steam-powered networks, through classic hot water systems (3rd generation), to today’s 4th and 5th generation systems, which operate with low temperatures and enable bidirectional energy exchange.
Transforming district heating into a CO₂-neutral system presents new and complex challenges for grid infrastructure worldwide. To achieve ambitious climate targets and integrate renewable energy sources effectively, district heating networks must continue to be developed both technologically and conceptually.
A key goal in decarbonising district heating networks is to lower operating temperatures. Doing so reduces heat losses, improves energy efficiency, and enables greater integration of renewable sources such as solar thermal energy and large heat pumps (source: IEA – International Energy Agency).
For example, many European cities are working towards “low-temperature district heating” systems to maximise compatibility with sustainable energy sources.
The integration of different energy sectors – electricity, heat, and mobility – is increasingly becoming standard practice. District heating networks act as a flexible interface, converting surplus renewable electricity into heat and storing it.
This sector coupling improves overall system efficiency and supports grid stability, as demonstrated by current pilot projects in Scandinavia and Central Europe.
Decarbonising district heating requires a broader mix of heat sources being fed into the grid. Alongside conventional power plants, industrial waste heat, geothermal energy, biomass, and solar thermal energy are increasingly being integrated.
This diversity places significant demands on the controllability and flexibility of system technology.
With the shift to lower operating temperatures and the integration of new energy sources, the demands on materials, network design, and system technology are increasing:
Decarbonising district heating therefore calls for a holistic approach to network design, material selection, and system integration.
The decarbonisation of district heating requires a systemic approach that combines renewable heat sources, innovative technologies, and forward-looking municipal planning. International comparisons highlight different areas of focus that can serve as blueprints for national and regional strategies:
A key lever for CO₂ reduction is the integration of renewable heat sources into existing and new district heating networks. Solar thermal systems can cover up to 50% of annual heat demand – particularly when combined with seasonal heat storage – as demonstrated in Denmark and Sweden. Geothermal energy provides low-carbon heat year-round, while industrial waste heat remains an underused resource that is increasingly being integrated into municipal heating networks.
Large heat pumps are gaining international importance by enhancing the flexibility of district heating systems and enabling direct coupling with the electricity sector. They use renewable electricity to raise heat from air, water, or waste heat to the required temperature. According to Heat Roadmap Europe scenarios, up to 25% of the energy fed into European district heating networks could come from heat pumps in the future, potentially reducing the sector’s CO₂ emissions by more than 70%. Large heat pumps also unlock low-temperature sources that were previously uneconomical.
Heat storage is essential to decouple generation and consumption and to balance the variability of renewable energy. Short-term storage systems, widely deployed in Denmark, enable flexible control of electricity and heat generation and efficient use of surplus energy. Seasonal storage – such as large earth basins or groundwater reservoirs – makes it possible to store solar heat generated in summer for use in winter.
In addition to renewable solid fuels and electricity, green gases (e.g. hydrogen or biogas) are being explored as complementary options to improve security of supply and flexibility. Power-to-heat technologies, such as electric or electrode boilers, can convert surplus renewable electricity directly into heat and feed it into the grid.
The transformation of district heating can only succeed through strategic municipal heat planning. This involves analysing current heat demand, identifying renewable energy potential, and developing a catalogue of measures for the gradual decarbonisation of district heating. In Germany, municipal heat planning has been a legal requirement since 2024 and serves as a blueprint for other countries aiming for systematic transformation.
Funding mechanisms at national and European levels – such as investment subsidies for heat pumps, storage systems, or network expansions – are essential to ensure the economic viability of the transition and to minimise investment risks.
The transformation of district heating into a low-CO₂ energy system places significant demands on grid infrastructure. Modern piping systems form the backbone of efficient, flexible, and future-proof heating networks. They not only enable the integration of renewable energy sources but also make a decisive contribution to reducing heat losses and ensuring operational safety.
The decarbonisation of district heating is a global goal, driven by a combination of legal requirements, subsidy programmes, and cross-sectoral cooperation in many countries. These measures provide the investment security needed to implement the transformation. Governments, international organisations, and local actors worldwide are therefore pursuing different, but increasingly ambitious, strategies to accelerate the transition to climate-friendly heating networks.
Utilities and grid operators are key players in implementing national and municipal decarbonisation strategies. They develop transformation plans, invest in new technologies, and coordinate the integration of renewable sources and the modernisation of infrastructure. In many countries, they are also obliged to report regularly on progress in emission reductions.
Manufacturers of system technology and piping systems – such as aquatherm – support the transformation with innovative, modular solutions tailored to the requirements of modern, low-CO₂ heating networks. They drive the development of new materials and technologies that increase the efficiency, durability, and flexibility of the networks.
The decarbonisation of district heating is technically feasible today, politically desired, and places high demands on the infrastructure. The efficiency and future viability of district heating systems depend largely on the quality of the network infrastructure. High-quality, optimally insulated piping systems minimise heat losses, increase operational reliability, and enable the flexible integration of renewable energy sources.
Modern system solutions – such as those from aquatherm – make an important contribution to the implementation of efficient, low-CO₂ heating networks. PP-R piping systems offer high corrosion resistance and allow for quick and safe installation. aquatherm's solutions help reliably meet practical requirements for temperature, pressure, durability, and installation. Projects such as the district heating networks in Gateshead (UK) and Veksø (DK) demonstrate that modern plastic pipes not only increase energy efficiency but also improve the CO₂ balance and the profitability of grid operation.
The decarbonisation of district heating is very close: it starts with you
Decarbonising district heating is a shared responsibility. Let the experts at aquatherm advise you individually: from planning to implementation, we support you with innovative, durable, and efficient piping systems for the district heating networks of the future.
