There are many renewable energy systems that are designed to make buildings more efficient, but which of them are best in terms of feasibility? To answer this question, the Institute for Building and Solar Technology (IGS) at Technische Universität Braunschweig undertook the study »future:solar – System Analysis for Solar Energy Supply«. (Prof. Dr.-Ing. M. Norbert Fisch, Mathias Schlosser, Thomas Willen, Robert Kellner)