This article takes an historical perspective on current attempts to ‘open up’ established, centralized systems of urban infrastructure to alternative technologies designed to minimize resource use and environmental pollution. The process of introducing alternative technologies into, or alongside, centralized urban infrastructures is not a novel phenomenon, as is often assumed. The physical and institutional entrenchment of large technical systems for urban energy, water or sanitation services in industrialized countries in the late 19th and early 20th centuries did not close the door completely on alternatives. I investigate a number of alternative technologies used in Berlin in the interwar period (1920–1939), in order to reveal the rationales developed around each technology and the ways in which each emerged, disappeared and re-emerged or survived across highly diverse political regimes. The selection of cases is guided by the desire to illustrate three different phenomena of alternative technology diffusion (and exclusion) experienced in Berlin: (1) technologies promoted by early pioneers and discarded by their successors (waste-to-energy), (2) technologies modifying traditional practices that were at odds with modernized systems (wastewater reuse for agriculture) and (3) technologies co-existing alongside the dominant centralized system throughout the 20th century (cogeneration). The empirical findings are interpreted with reference to their contribution to scholarship on urban socio-technical transitions.