Saving fossil fuel, reducing operating costs, increasing efficiency.Around a third of the world’s primary energy is used to operate buildings. Fossil, non-renewable fuels are used for more than 80 percent of this, while the demand for energy is growing at the same time. Energy is usually generated in large central power plants, and the energy is provided via wasteful supply networks. Decentralized energy generation seems more than logical. In addition to solutions to use energy more efficiently and reduce consumption, renewable energy sources must increasingly be developed. Priedemann considers locally usable solar energy in particular to be one of the most sensible solutions.