The MUSE model (the ModUlar energy systems Simulation Environment), the new modelling environment developed at Imperial College London, simulates plausible pathways of the energy systems transition to a low-carbon economy on a global scale. The model simulates the behaviour of real investors, including under different decarbonisation scenarios. This seminar will first discuss the distinctive features of MUSE in the context of energy systems models, highlighting its scope, modularity, flexibility, and technological detail. A particular focus of the presentation will be on the methodology used in the building sector module which will discuss diffusion of technologies in the UK. Energy-related investment decisions in the residential sector are complex and heterogeneous in the sense that they are not based on one specific criteria, but rather a range of drivers of consumer behaviour. Given these challenges, the modelling approach includes agent-based methods to determine energy related investment decision-making, explicitly characterizing the ability of people to gather information, evaluate the options, and choose among alternatives. A case study is presented which illustrates the attributes of the approach for the residential building sector in the UK, which has strong decarbonisation targets.