Salzburg, a pioneer in sustainable urban development, is transforming into a model for renewable energy integration and smart city innovation. Leveraging its status as a Smart Grids Model Region, Salzburg is implementing a wide array of emission-reducing initiatives aimed at climate protection. Central to this effort is the city's vision for 2050, outlined in a comprehensive master plan that lays out a path towards becoming a Smart City. This transformation involves expanding and optimizing the district heating grid, increasing the use of renewable energy sources, drastically reducing energy consumption in buildings, and offering new mobility options. A cornerstone of Salzburg’s renewable energy strategy is the innovative use of solar power in the Lehen district. This area has been the focus of extensive redevelopment since 2007 as part of the EU initiative Concerto II “Green Solar Cities.” The project encompasses the construction of 287 rental apartments, a city gallery, a student hostel, and a nursery school on the former site of the municipal utilities company. Additionally, an existing office block has been renovated to house modern offices, laboratories, and conference rooms. The adjacent Strubergassensiedlung neighborhood has also undergone significant renovation, employing the latest technologies to enhance energy efficiency. This showcase project, known as Stadtwerk Lehen, exemplifies how well Salzburg’s renewable energies industry has adopted and implemented Austria's sustainable energy strategies. The energy infrastructure at Stadtwerk Lehen integrates district heating with advanced solar energy systems. A thermal solar facility, featuring a 2,000 square meter collector area, plays a pivotal role. This facility channels heat into a central storage unit with a 200,000-liter capacity. To boost efficiency, a solar heat pump is incorporated, increasing output by an additional 15 to 20 percent. The system distributes heat through a low-temperature microgrid to both flats and offices within Stadtwerk Lehen and to nearby renovated apartment blocks.