[en] This paper examines the role of energy efficiency and non-economic factors such as consumers' preferences, lifestyles and values (which have hitherto been ignored) in energy demand and CO_2 emissions modelling for Nigeria. We use a structural time series model to estimate various energy demand and CO_2 intensity models that take account of the aforementioned factors. We adopt preferred models from these estimates to analyse how energy demand and CO_2 emissions in Nigeria might evolve by generating three different future scenarios to 2025. We find energy efficiency and non-economic factors to influence energy demand and CO_2 emissions. The long-run income and price elasticities obtained differ significantly from those in existing studies that have ignored these salient factors. In a business-as-usual scenario, the results indicate that energy demand will continue to grow. Consequently, present policies do not sufficiently mitigate aggregate CO_2 emissions in Nigeria. The lesson for policy makers is that the extant policies introduced to restrain CO_2 emissions (from a production perspective) have to be combined with new policies that influence consumers' lifestyles and behaviours, develop energy efficient technologies and apply low tariffs on imported energy efficient appliances, to drive down CO_2 emissions from a consumption perspective. - Highlights: • We model energy demand and CO_2 emissions for Nigeria during 1971–2012. • We examine the role of energy efficiency and other non-economic factors (ExNEF). • We found energy efficiency and ExNEF to be significant determinants in the model. • Existing policies to restrain CO_2 emissions (from a production side) are insufficient. • Environmental policies also need to restrain CO_2 emissions (from a consumption side).