Through mostly empirical research, Gregory examines innovation processes and governance strategies for transitioning to a sustainable energy system, for diffusing new technologies, and for advancing urban sustainability. At present, his research is focused on the governance of fossil-fuel industries (including divestment and phase-outs) and the diffusion of hydrogen and fuel-cell technologies. With a focus on countries such as Japan, USA (California), China, Germany and Indonesia, he is currently investigating energy topics such as the political economy of coal, strategies for accelerating the diffusion of fuel-cell vehicles and renewable hydrogen, and policies mixes for phasing-out unsustainable energy and road transport technologies. Gregory sits on the editorial board of Energy Research and Social Science as well as Frontiers in Sustainable Cities and has published over 20 peer reviewed papers in leading journals such as Renewable and Sustainable Energy Reviews, Energy Policy, Energy Research and Social Science, Global Environmental Change, Journal of Cleaner Production, Environmental Science and Policy and Technological Forecasting and Social Change.