Preliminary investigations into the energy efficiency of manufacturing firms operating in South Africa have shown that no previous study of the barriers to energy efficiency has been conducted. This paper sets out to investigate whether there is an energy efficiency gap in medium to large manufacturing firms operating in the eThekwini municipal area. It goes on further to analyse the barriers to energy efficiency in such firms. These barriers are analysed by firm characteristics and across manufacturing sectors. The findings of this research indicate that more can be done to improve the energy efficiency profile within South African manufacturing subsectors. Policy-makers should take these findings into consideration when drafting new policy on energy efficiency.