Heat provision to buildings constitutes a complex system to govern due to its interdependencies with the surrounding energy system, its relations to political objectives and the longsighted character of investments. This chapter investigates how heat provision in Denmark has been rendered intelligible as a governable system by means of a market imitating knowledge assemblage developed and controlled by national governance actors. We analyse how future price signals are rendered into fact-like entities within this knowledge assemblage through the specification of a network of contentious analytical assumptions. Finally, we show how this knowledge assemblage constitutes a barrier to organised low-carbon governance of heat provision and how urban actors attempt to reconfigure assumptions in support of such low-carbon governance. The study demonstrates how carbon politics is embedded in the nuts and bolts of the knowledge assemblages by which heat provision is rendered intelligible as a governable system.