By Herbert Hemis, City of Vienna


The city of Vienna and its wholly-owned energy provider are testing a range of participatory approaches to meet the city’s decarbonisation goals. From sustainable urban planning, through geothermal engineering to blockchain technology, Vienna is contributing new ideas and sustainable solutions for the city of tomorrow.

 The city of Vienna is Austria’s cultural and economic centre. The metropolitan area houses almost a third of Austria’s 8.9 million inhabitants. Vienna is also on track to becoming the country’s centre for green energy: by 2050, the city aims to meet half its energy consumption from renewable sources – and be close to fully decarbonised for heating and cooling.

These and other goals are in the Smart City Vienna Framework Strategy 2019-2050[1]. Other strategies, like the Energy Framework Strategy 2030,[2] the Urban Development Plan and the Climate Protection Programme share this perspective. There are many approaches towards decarbonisation taking place. Here we will present three: new energy zoning plans, new methods of energy supply for heating and cooling, and finally some initiatives of the city-owned provider, Wien Energie, including citizen-owned power plants and the decarbonisation of district heating.

Energy zoning plans – a new energy planning instrument

Energy should be a part of urban planning. The Energy Zoning Planning Concept (“Fachkonzept Energieraumplanung”), part of the Urban Development Plan, was implemented in 2019[3] to guide the city to integrate energy in different planning issues. Among other measures, it introduced energy zoning plans, developed by the Department for Energy Planning. Just like land use zoning plans or building regulation plans, the energy zoning plans set out the energy solutions for heating and hot water supply for defined zones. All new buildings in the zones must use district heating or other high-efficiency solutions like renewables or waste heat. This enables the steering of a more efficient use of district heating in the city and prevents fossil gas solutions for new buildings. Finally, it could enforce innovative solutions, such as micro-heat networks with low temperature sources.

Energy Zone Map of Vienna
Figure: Energy zoning plans: in the orange zones, only high-efficiency energy solutions for new buildings are allowed. Source: City of Vienna – Department for Energy Planning

The first energy zoning plans for three districts will be approved by the City Council in June 2020. Energy zoning planning for all 23 districts will be complete in 2021.

The Department for Energy Planning is working on upgrading the energy zoning plans through extending the regulations for the building stock. There are many buildings which are connected to gas and district heating or have different energy systems for each apartment. It is more efficient to use just one system in one building and in some areas, it is possible to find cross-building solutions so that renewable generation, energy demand and energy storage are linked up. The biggest challenge for decarbonisation is the transformation of the building stock ― to switch from a fossil energy system to renewables or high-efficiency systems.

Innovative approaches for heating and cooling

Housing (especially heating) and transport are responsible for 90% of Vienna’s energy consumption, which is why the city administration is especially eager to cut down emissions in these sectors.

Vienna’s municipality owns 220,000 apartments ― more than any other municipality worldwide― many of which are now being remodelled to become more energy-efficient. All new buildings constructed under the subsidised housing programme, as well as all new school buildings, will run on 100% renewable energy. Similarly, ambitious plans exist for the transport sector: the city is investing in public transport and cycle lanes, with the aim that by 2030, eco-friendly modes of transport will make up 85% of the total.

 MGG22 shows the way[4]

Apartment complex MGG22 is an example of the new approach. A residential complex of about 155 apartments, located in Vienna’s 22nd district, MGG22 has an innovative energy system.

The estate is heated and cooled using geothermal and wind energy. As overheating in summer is a growing problem in residential buildings, attention was specifically paid to summer suitability during the planning process. The entire building is kept at a temperature between 21°C and 27°C throughout the year. To achieve these temperatures, the building’s concrete ceilings store heat: they are heated using geothermal energy. Some 50 vertical probes were drilled up to 150 metres into the ground, where the temperature is a constant 5°C to 15°C all year round.

The temperature of the source, the rooms and the hot water are maintained by the efficient use of a reversible heat pump: in winter, heat is extracted from the ground and in summer, this energy is returned to it.

The heat pump is powered by wind energy. In windy conditions, excess wind power that would normally put a strain on the electrical distribution networks is used to heat the buildings. Both residents and wind farm operators benefit, since residents profit from low energy costs and wind farm operators from being able to operate their turbines continuously without having to make compensation payments to the grid operator.

MGG22 Complex
The MGG22 apartment complex uses a low-temperature system for heating and cooling provided by renewables. Credit: https://www.mgg22.at/

The energy costs for an apartment in MGG22 will be less than half of those for a conventional apartment. Air conditioning systems, which are being used more and more in apartments with conventional heating systems, are not needed. This reduces the energy costs for tenants and avoids emitting additional heating into the outdoor air. The city of Vienna now also enforces such solutions in the social and subsidized housing programme. Furthermore, some developers and construction companies are developing and using similar approaches.

Citizen-owned solar and wind power plants

The 100% city-owned energy provider Wien Energie is also devising innovative strategies for a participatory energy transition. New non-residential buildings have been required to install solar energy (0.7 kilowatt peak per 100 m² gross floor area) for some years. From 2020 onwards, this regulation is extended to residential buildings. Many of Vienna’s residents live in flats and are therefore unable to set up solar energy panels on their rooftops. Wien Energie solved that issue by handing the ownership of its solar and wind power plants to residents. Starting in 2012, Wien Energie had built wind turbines and installed solar panels on the roofs of large buildings, such as shopping centres, and in industrial areas such as the old Vienna harbour.

Any resident could buy a maximum of ten panels or shares in the wind project, costing around €250 – 950 per share or panel depending on the project. The panels are leased back to Wien Energie, which is responsible for maintenance and the distribution of the generated energy. In return, the owners receive interest every year, which they can choose to have in the form of supermarket vouchers, an option that was so popular it sold out within 72 hours. Once the panels reach the end of their lifetime, Wien Energie will buy them back for the original amount invested.[5]

Wien Energie’s newest and largest citizen’s solar project is built on a drinking water reservoir in Unterlaa, with 6,400 solar panels producing around 2.05 gigawatt hours a year. Construction is complete and it will come into operation in spring 2020. Part of the generated energy will be used for the reservoir. Private customers of Wien Energie can buy a maximum of three shares for €250 per share. They can redeem their vouchers at a supermarket or use them to pay their electricity bills. The customer will get vouchers for each share with a value of €60 each year for five years. This is nearly equivalent to 6.4% annual return.

In total, a stunning 10,000 residents participated in the projects between 2012 and 2017, investing €35 million into 26 solar and four wind power plants. The installations produced 50,000 MWh, equal to the annual consumption of 550,000 fridges, and saved around 17,000 tonnes of carbon dioxide. The project was so successful that it is now being expanded to include e-charging stations, with a target of 1,000 stations to be constructed and sold by 2020.

Cutting emissions in the housing sector

A special project is the newly constructed green living and working quarter, Viertel Zwei, near the city centre, bordering an artificial lake and a park, where Wien Energie is testing a number of innovative projects. The company lets electricity customers choose between three energy tariffs to enable them to optimise their costs and consumption. The residents are encouraged to provide feedback in order to further improve the tariffs. Some of Viertel Zwei’s residents can contribute to Wien Energie’s vision of a smart urban future by selling surplus energy generated by PV installations on their rooftops to their neighbours, using blockchain technology.[6]

Viertel Zwei
Viertel 2. Credit: Wojtek Gurak on Flickr

While Viertel Zwei is home to some of Vienna’s wealthier residents, Wien Energie also has projects aimed at lower-income households. Despite being a comparatively wealthy city, between 68,000[7] and 99,000[8] people are affected by energy poverty. Wien Energie therefore appointed an ombudsman to assist people who are unable to pay their energy bills or heat their homes. The ombudsman gives people advice on how to reduce their energy consumption. Some measures, such as insolation and changing the windows, are subsidised by the city. This programme has helped around 20,000 residents since 2011.

The future of district heating

Wien Energie operates a 1,200-kilometre-long district heating network in Vienna, with an installed capacity of around 2,500 MW, supplying around 35% of all apartments and more than 6,000 business customers.  The main source is the waste heat from the combined heat and power plants and waste incineration.

Wien Energie wants to increase the share of renewables for district heating as well as provide innovative separated small networks. A research project, GeoTiefWien, is looking for hot water reservoirs in the subsoil – especially in the Eastern part of the city.  This could contribute significantly to Vienna’s goal of raising the renewable share in the district heating grid from the current 18% to 40% by 2030. Solar power and biomass should also play a bigger part in future. Nevertheless, it is also necessary to increase the efficiency of the network while decreasing the temperature of the hot water in the network and increasing the connection rate to buildings in areas where district heating pipes are already available. Furthermore, the line that returns the energy to the district heating network, which has a lower temperature (60°C) as the supply line (80-90°C), could be used for heating new buildings.

Conclusion: A smart, innovative, and participatory transition

Vienna has introduced unique projects to ensure that the energy transition takes place and that residents are actively involved. Energy zoning plans could be an instrument for a city to steer pipe-bound infrastructure like district heating/green gas/exergy networks and to enforce the transformation of the building stock from fossil solutions to renewables. Innovative approaches are showing that cooling and heating can be combined in one system, with low costs. Resident-owned solar and wind power plants can be a role model for other cities looking for ways to include residents in the generation of renewable energy. It also shows how public ownership can enable and speed up the energy transition. For people with their own solar panels, the use of blockchain technology to sell surplus energy is an innovative experiment.


About the author:

Herbert Hemis is an energy planning expert, based in the City of Vienna since 2015. He is connecting the fields of energy and urban planning. He works also as project assistant on EU-funded projects (Smarter Together, Urban Learning, Decarb City Pipes) as well as national-funded projects. The experiences of these projects will be integrated in the tasks of the City and vice versa. Two main tasks at the moment are the development of energy zoning plans and generating energy data models like a heat atlas for the city. He previously worked in the private sector and in research for the Technical University of Vienna.

This blog article is co-created by Josephine Valeske and part of the mPOWER blog series in which cities and towns share how they are building better energy futures.

Featured image: The biggest citizen’s solar power plants in Unterlaa. Credit: Wien Energie


[1] Smart City Wien Framework Strategy 2019-2050: https://smartcity.wien.gv.at/site/en/approach/framework-strategy/

[2] Energy Framework Strategy 2030: https://www.wien.gv.at/stadtentwicklung/energie/pdf/energierahmenstrategie-2030-en.pdf

[3] Energy Zoning Planning Concept:
https://www.wien.gv.at/stadtentwicklung/energie/pdf/energy-zoning-planning.pdf

[4] Information provided by Thomas Kreitmayer, Department for Energy Planning, City of Vienna. More Information about the building project MGG22 (in German): https://www.mgg22.at/

[5]  https://energy-cities.eu/best-practice/citizens-solar-power-plant/

[6] More information about Viertel Zwei (in German): https://hlk.co.at/a/im-viertel-zwei-handeln-bewohner-mit-strom or https://blog.wienenergie.at/2020/05/08/energiegemeinschaft-im-graetzl/?utm_campaign=klimaschuetzen&utm_medium=cmplp

[7] Information about energy poverty and energy consulting provided by the city of Vienna: https://www.wien.gv.at/stadtentwicklung/energie/energieberatung-armutsgefaehrdet.html

[8] https://wien.arbeiterkammer.at/interessenvertretung/wirtschaft/energiepolitik/Energiearmut_bekaempfen.html