Primary aluminium production is a highly energy-intensive and greenhouse gas (GHG)-emitting process responsible for about 1 % of global GHG emissions. In 2009, the two most energy-intensive processes in primary aluminium production, alumina refining and aluminium smelting consumed 3.1 EJ, of which 2 EJ was electricity for aluminium smelting, about 8 % of the electricity use in the global industrial sector. The demand for aluminium is expected to increase significantly over the next decades, continuing the upward trend in energy use and GHGs. The wide implementation of energy efficiency measures can cut down GHG emissions and assist in the transition towards a more sustainable primary aluminium industry. In this study, 22 currently available energy efficiency measures are assessed, and cost-supply curves are constructed to determine the technical and the cost-effective energy and GHG savings potentials. The implementation of all measures was estimated to reduce the 2050 primary energy use by 31 % in alumina refining and by 9 % in primary aluminium production (excluding alumina refining) when compared to a “frozen efficiency” scenario. When compared to a “business-as-usual” (BAU) scenario, the identified energy savings potentials are lower, 12 and 0.9 % for alumina refining and primary aluminium production (excluding alumina refining), respectively. Currently available technologies have the potential to significantly reduce the energy use for alumina refining while in the case of aluminium smelting, if no new technologies become available in the future, the energy and GHG savings potentials will be limited.