This article was published in the journal, Energy Policy (Special Section: Transition Pathways to a Low Carbon Economy) [© Elsevier Ltd.] and the definitive version is available at: http://dx.doi.org/10.1016/j.enpol.2012.08.040This paper explores the possible evolution of UK electricity demand as we move along three potential transition pathways to a low carbon economy in 2050. The shift away from fossil fuels through the electrification of demand is discussed, particularly through the uptake of heat pumps and electric vehicles in the domestic and passenger transport sectors. Developments in the way people and institutions may use energy along each of the pathways are also considered and provide a rationale for the quantification of future annual electricity demands in various broad sectors. The paper then presents detailed modelling of hourly balancing of these demands in the context of potential low carbon generation mixes associated with the three pathways. In all cases, hourly balancing is shown to be a significant challenge. To minimise the need for conventional generation to operate with very low capacity factors, a variety of demand side participation measures are modelled and shown to provide significant benefits. Lastly, projections of operational greenhouse gas emissions from the UK and the imports of fossil fuels to the UK for each of the three pathways are presented