The central aim of this thesis is to identify a route to achieve 60% carbon savings in the UK domestic sector by 2050. This has led to two key questions: Is a strategy of relying largely on improvements in energy efficiency likely to achieve the required savings If not, could personal carbon rations offer an alternative route To answer the first question, both the past record and future projections of savings from energy efficiency are investigated. Thirty years of energy efficiency improvements have led to an increase of a third in final energy use, due to a contemporaneous increase in demand for energy services. A bottom-up energy model shows that even modest social and behavioural changes could lead to a future increase in energy consumption of 23% by 2050. In combination with these demand increases, even maximum implementation of energy efficiency measures could only deliver a 17% saving. Policies for improving energy efficiency do nothing to restrain demand for energy services, and this makes it very unlikely they, alone, can deliver 60% carbon savings by 2050. This thesis proposes that personal carbon rationing, for household and personal transport energy, would provide a framework for guaranteed and equitable carbon reductions, within a context of global carbon reductions. Each person would get an equal ration which would reduce over time. Equal carbon rations would not affect everyone equally because emissions currently vary considerably between groups and individuals. Personal carbon emissions for 32 case study individuals varied by a factor of 12. Therefore a variety of responses to rationing will be required, and energy efficiency will remain an important strategy within the rationing framework. It is concluded that personal carbon rations have considerable promise for achieving 60% savings by 2050.