Across Western electricity systems, private households are increasingly engaging in the micro-generation of electricity. Previously traditional end-users of electricity consumers are utilizing the opportunities made possible by technical developments in photovoltaics and wind turbines, becoming prosumers: small-scale end-users who, in addition to using electricity from the grid, generate power for own consumption and/or to be fed back into the grid. By addressing the research question “what factors enable or constrain developments in prosumer figures in national electricity systems?” the report maps incentive structures (support schemes); direct regulatory requirements; and information practices and market availability, while controlling for national characteristics of the three countries. It finds that that the most important single factor for increasing prosumer numbers is the existence of a stable, robust and generous support scheme. Natural characteristics such as the need for reducing carbon emissions is a significant background factor, as are bureaucratic hurdles, and third party market availability for technical solutions for consumers who are considering becoming prosumers.