In moving towards sustainable heating systems, one key element is use of waste heat in dwellings and other buildings. Compared with today, there will be less industrial waste heat available in the future as industries become substantially more efficient, downsize or disappear. While geothermal heat is a renewable source, its long-term potential is anything but clear. Against this background, Friends of the Earth-Netherlands asked CE Delft to analyse the availability of sustainable heat for urban heating in 2030 and 2050, in the form of geothermal heat or industrial waste heat from ‘sustainabilized’ industry.