This paper describes a case study of an energy efficiency project carried out for a UK manufacturer of ready meals. As well as a review of relevant literature the study collected and analysed data on energy and water use and analysed the possible use of waste heat in the effluent from the factory. The novelty in this project was the use of building simulation software to model the impact of modified temperature control, solar thermal collectors and absorption chillers on factory energy use. The results show the weather dependence of energy used by food factories where electrical energy is dominated by refrigeration, and the poor correlation of gas use with output due to the use of large volumes of hot water for cleaning.