Heat for another 16,000 households from the waste incineration plant in Spittelau

A new large-scale heat pump at the Vienna Spittelau waste incineration plant will heat 16,000 Viennese residents in future. An additional 16 megawatts of power will increase the efficiency of waste incineration by 13 percent. The plant is a ThermaFLEX demonstration project in the Green Energy Lab portfolio.

© Wien Energie

Wien Energie is building the third large heat pump in Vienna at the Spittelau waste incineration plant. Thanks to its sophisticated technology, this innovative project is unique in Central Europe. With an output of 16 megawatts, the state-of-the-art plant will supply around 16,000 households with climate-friendly district heating from spring 2025, saving around 22,000 tons of CO2yearly.

Climate neutrality: district heating is becoming increasingly important

Vienna has set itself the goal of being climate-neutral by 2040. Switching to environmentally friendly forms of heating is a key success factor here. District heating is becoming increasingly important: 56 percent of Vienna’s heating requirements are to be covered by district heating by 2040. In order to generate exclusively climate-neutral district heating in the future, Wien Energie is relying on the use of existing waste heat in addition to geothermal energy.

“The new large heat pump is an important milestone for our heat transition. With the investment of around 40 million euros in this highly innovative solution for the maximum use of existing waste heat, we are at the forefront of technology and are setting standards throughout Europe. When it goes into operation in 2025, we will not only supply an additional 16,000 households with district heating, but will also make Spittelau the most efficient waste incineration plant in Central Europe”, says Karl Gruber, Managing Director of Wien Energie. The heat pumps increase the efficiency of the entire waste incineration plant by around 13 percent to over 95 percent. This means that almost all the energy required for the process is used efficiently.

Waste heat from flue gas cleaning heats up and conserves water resources

Wien Energie generates electricity and heat at the Spittelau waste incineration plant. Flue gases are produced during the combustion process. These are filtered and cleaned in a multi-stage process, including in a so-called wet flue gas scrubber. Pollutants from the flue gas are bound in the water. The water is then purified in a complex process, cooled and released back into the Danube Canal as purified water. The waste heat remains in the flue gas and is released into the air via the chimney.

From the beginning of 2025, this will change: Wien Energie will use this waste heat for the additional generation of district heating using heat pumps. Heat exchangers are used to extract around 10 degrees Celsius from the condensate (water) produced when the flue gas is cooled and this energy is used with modern heat pump technology in the highly complex system to generate heat at around 90 degrees Celsius. This heat then flows in the form of hot water via the district heating network into tens of thousands of Viennese homes.

The cooled water from the flue gas condensation is treated again and fed back into the waste incineration plant process. As a result, Wien Energie needs up to 125,000 cubic meters less water per year from the Danube Canal for the waste incineration process – roughly equivalent to 700,000 bathtub fillings.

Infographic large heat pump Spittelau – Photo: Wien Energie / APA Grafik


Decarbonization of district heating with waste heat and geothermal energy

District heating is to become completely climate-neutral by 2040. Large heat pumps and geothermal energy are primarily used for this purpose. A good half of Vienna’s district heating currently comes from combined heat and power plants that run on natural gas. Cogeneration plants are also used to cover peak demand (less than 10 percent). Around a third comes from waste incineration, the rest from industrial waste heat, biomass and geothermal and ambient heat. By 2030, more than half of district heating is to come from renewable sources and by 2040 Wien Energie aims to generate all of its district heating from renewable energy.

The Spittelau large-scale heat pump is Wien Energie’s third large-scale heat pump project with an output of over 10 megawatts. The first plant went into operation in 2019 at the Simmering power plant site, where it uses residual heat from the cooling water circuit. The second system is nearing completion: Wien Energie is currently building the largest and most powerful large-scale heat pump in Europe at the ebs wien sewage treatment plant in Simmering. When fully completed, the plant will supply 112,000 households with climate-neutral heat. Wien Energie has already installed two further, smaller large heat pumps for waste heat utilization at UNO-City and Therme Wien.

Key data large heat pump Spittelau

  • Construction start: Spring 2023
  • Planned commissioning: Beginning of 2025
  • System output: 16 megawatts thermal (2 heat pumps of 8 MW each)
  • Households supplied: around 16,000 Viennese households
  • CO2 savings: around 22,000 tons of CO2/year
  • Investments: 40 million euros
  • The project is funded by the Climate and Energy Fund and carried out as part of the RTI initiative “Vorzeigeregion Energie” as part of Green Energy Lab’s flagship project “ThermaFLEX“. In June 2023, ThermaFLEX was awarded the “Best of the Best” prize for outstanding performance. Energy Globe Austria Award.

About the Spittelau waste incineration plant

The Spittelau waste incineration plant is a Viennese landmark and a role model for climate protection in the city. With the redesign by the artist Friedensreich Hundertwasser after a major fire, the plant has been combining technology, art and ecology for over 25 years. The site has one of the world’s most modern flue gas purification systems and recycles waste to the highest environmental standards. 250,000 tons of Viennese household waste are incinerated here every year. The heat generated at Spittelau heats more than 60,000 households in Vienna every year. 50,000 households can be supplied with electricity.


Delivery of the new large heat pump at the Vienna Spittelau waste incineration plant

Image: Wien Energie


With an output of 16 megawatts, the heat pump will supply 16,000 households in Vienna with district heating in future, increasing the efficiency of the waste incineration plant to over 95 percent

Image: Wien Energie/Johannes Zinner


Excursion by the Green Energy Lab team to the Spittelau waste incineration plant

Image: Green Energy Lab



Ludwig Fliesser

Communications Manager

T: +43 676 47 19 347
E: ludwig.fliesser@greenenergylab.at