Energy transitions are in many respects past the early exploration stages and moving towards the urgently needed mass market take-up. We examine the Finnish energy transition regarding how solutions – heat-pumps, deep retrofits and new district-wide solutions – that have demonstrated economic benefits and reasonable payback times have faced slow uptake and slow market development. We focus on the difficulties that suppliers and adopters face in establishing the value and singularization of goods when adopters need to act as calculative agents in the market. When the intermediation processes needed for market development do not cover the all the needed aspects, these market difficulties can persist until late in the transition process. We further elaborate how the intermediation takes place in ecologies of actors that become complex once the complexity of goods grows and the intermediation becomes tied to formalized arenas such as those found in urban development. Periodic assessment of the effectiveness of markets and ecologies of intermediation can inform policy interventions on market development.