Energy Efficiency Solutions

All three Lighthouse Cities have made great strides towards becoming more energy efficient. To this end, the cities have built new infrastructure and upgraded existing solutions – each more impressive than the next!


  • Retrofitting – 26 buildings (including 302 dwellings) in the Coronación neighborhood, the city’s most vulnerable neighbourhood, were retrofitted to become energy-efficient. This included the insulation of façades and roofs as well as installing double windows or replacing the existing ones. The district was connected to the new biomass-based district heating system. Overcoming considerable barriers in citizen engagement and community involvement, the retrofitting was a success, reducing not only energy consumption (up to 50% kWh/year, leading to 20% savings in household energy bills) but providing residents with modern, heated, and smart homes.
  • The biomass district heating system – this novel heating system in Vitoria-Gasteiz services around 300 dwellings in the Coronación demo district with the opportunity to extend it to other neighbourhoods. As homes generally tend to have individual boilers based on natural gas, this solution was crucial in terms of promoting district heating culture in Vitoria-Gasteiz. The estimated installed power is 3,200 kW – all generated from biomass! The system has many benefits, such as reduced consumption, maintenance and operation costs, less carbon emissions, and reduced energy bills for the consumers.


  • Retrofitting – 18 Soviet era apartment buildings in the downtown area of Tartu were renovated into smart, energy-efficient dwellings. During the project, the buildings (incl. roofs and basements) were completely renovated and insulated, new triple-glazed windows installed, central heating systems reconstructed, PV panels installed and all apartments were equipped with smart sensors and meters and a smart home system for monitoring energy consumption and controlling the indoor climate. So far, this retrofitting package has resulted in a ca. 60% reduction in energy consumption!  All buildings, with the help of art curators, also chose an original artwork to decorate the dwelling (either a mural or sculpture).
  • District cooling station– a whole new district cooling station was constructed in Tartu in 2016 by Grenthat uses residual heat for producing water, which is supplied through the existing district heating network. More specifically, this system is based on a heat pump that, installed to return the flow of the district cooling system, produces heat for the district heating system by using residual heat from cooling. The district cooling station also uses free solar energy from PV panels to cover a part of the cooling system’s energy demand.
  • LED lights with smart controllers – the pilot area of Tartu received new LED street lighting with smart controllers. The new lights are equipped with various sensors and can analyze traffic volumes and flows, road conditions, noise levels and various environmental data such as pollution, temperature, humidity, etc. The new lights save up to 80% more energy!


  • Retrofitting – 7 different social housing departments with 51 buildings (including 815 apartments) were retrofitted with different measures, which include insulation, new ventilation with heat recovery, new LED lighting both indoors and on the street, automatic heating control systems in the district heating supply of buildings, improvements to indoor climate and PV panel installation. The retrofitting achieved energy savings of up to 47%!
  • Solar cells with battery storage – 1,639 apartments were connected to PVs with battery systems on the rooftops of the housing association buildings in Sonderborg. As the price for selling solar electricity to the public grid is low, it made more sense to help the residents use the generated electricity directly in their homes. For this, solar cells with batteries were installed, enabling energy savings for the residents and for them to use the energy stored during the day even at night, which helps reduce the peak load demand on the public grid.

How to use & tips


Read our Travel Guide for Cities to see what worked and what did not with these solutions, or go directly to our worst practices to see our most important learning points.

Links to more information

Find the city solutions here - City Solutions / 
Read the Vitoria-Gasteiz reports here – Vitoria-Gasteiz demo intervention summary report , Building retrofitting interventions completed and District heating network deployed and in use 
Read the Tartu reports here – Building retrofitting completed , District heating and district cooling system is commissioned and deployed and Street lighting 
Read the Sonderborg reports here – Sonderborg demo intervention summary report and Sonderborg building retrofitting complete