District heating has been around for almost 150 years. Since the first commercial system was installed in New York in 1877, district heating systems have used insulated supply and return pipes to distribute heat to multiple buildings. While the first generation used steam produced by a central fossil fuel boiler, modern systems have evolved into a flexible infrastructure that can connect multiple energy and storage solutions and supply both heating and cooling. This way, they keep up with and actively sustain the rapidly changing global energy system, marked by rising electricity demand and a growing share of renewables.
Today, district heating supplies around 10% of global building heat demand, with much higher shares in Northern and Eastern Europe and China, and growing deployment in newer markets such as Canada and Ireland. Around 90% of global district heating supply is produced from fossil fuels today. The infrastructure can enable large-scale integration of renewable and other low-emissions sources, such as bioenergy, solar thermal and geothermal energy, and nuclear energy. While only a small part of networks already operates at low-temperature levels that make renewable integration straightforward, ongoing upgrades to pipes, substations, and controls will be critical to unlocking greater flexibility and efficiency.
Particularly valuable in dense urban areas, district heating networks offer benefits beyond renewable and storage integration, including easier infrastructure management, efficient use of space, recovery of waste heat, and lower local air pollution.
This commentary examines key emerging opportunities that could strengthen the role of district heating in the changing energy landscape, expanding heat recovery and enabling system flexibility.
Illustration of selected heat sources available to a district heating system
Available waste heat from sources such as data centres, industry or wastewater can be leveraged to heat both residential and commercial buildings using district heating networks
Recovering more waste heat streams from new and untapped heat sources unlocks efficiency gains
District heating is the most efficient - and sometimes only - technology available to recover heat streams that otherwise would go to waste. As such, they can play an important role in enhancing energy efficiency in a system. While high-temperature waste heat is often already recovered in industries or utilised for power generation, a large volume of waste heat below 100 °C is still discharged into the environment. Modern district heating networks can operate at lower temperatures and integrate a wide range of heat sources while minimising distribution losses. Growing electricity consumers in the future energy system, such as data centres or hydrogen electrolysers, generate low-temperature waste heat and increase opportunities for recovery if located close enough to urban areas. The use of heat pumps to upgrade low-temperature waste heat to higher temperatures suitable for district heat distribution further enables the effective use of otherwise unusable heat sources, such as wastewater or mine water from decommissioned coal mines.
