High-resolution stochastic ‘bottom-up’ domestic energy demand models can be used to assess the impact of low-carbon technologies, and can underpin energy analyses of aggregations of dwellings. The domestic electricity demand model developed by Loughborough University has these features and accounts for lighting, appliance usage, and photovoltaic micro-generation. Work is underway at Loughborough to extend the existing model into an integrated thermal-electrical domestic demand model that can provide a suitable basis for modelling the impact of low-carbon heating technologies. This paper describes the development of one of the new components of the integrated model: a solar thermal collector model that provides domestic hot water to the dwelling. The paper describes the overall architecture of the solar thermal model and how it integrates with the broader thermal model, and includes a description of the control logic and thermal-electrical equivalent network used to model the solar collector heat output.