James' research focuses on modelling future low carbon energy systems both nationally for the UK and globally. For the former he uses UK TIMES, which was developed at UCL and is now the UK Government's core energy system model, and the high spatial and temporal resolution electricity system model (highRES), which he co-developed. For the latter he use the Times Integrated Assessment TIAM-UCL.
James is particularly interested in transitions to highly renewable energy systems which are socially and environmentally sustainable. This led to the development of highRES which, with its hourly time and 50km by 30km spatial resolution, is ideally suited to understand how to integrate renewables into Great Britain's energy system. He has also recently been involved in various efforts looking at uncertainty in energy system models.