This work is concerned with the analysis of industrial energy use for the purposes of reducing that use to a minimum within the constraints imposed by the existing plant. The work is divided into two parts. Firstly, a general analysis of the energy used in an industrial plant is made for the year 1986. Based on monthly records of energy consumption and environmental parameters, it is primarily intended to heighten management awareness of energy flows and the relative contributions from each energy type towards the total annual consumption and cost. It is performed using a suite of interactive linked computer programs and the data is reduced to a graphical form for presentation in a report. The analysis is a first approximation, assuming steady state conditions with many parameters time and space averaged, but is justified by the findings that monetary savings approaching 5% of the annual energy bill could be made with changes to operational procedures alone. As a result of this work, it was revealed that the boiler-house supplying the majority of the plant with high pressure hot water for process and space heating requirements used more than half of the total annual energy requirements and that potential energy savings were likely. Secondly, a detailed analysis of the energy used by the boiler-house is- carried out. A real time monitoring and targeting system which records and displays boiler, environmental and plant parameters is developed and installed. Data gathered over a period of six months enables (i) specific cases of energy wastage resulting from operational procedures to be identified and (ii) trends of performance indicating poor energy efficiency to be traced. The system developed may be used to provide the information necessary to enable improved control. A general result which may be inferred from this work would be that the combined approaches of a topdown general analysis and a bottom-up detailed analysis of energy use can provide significant opportunities for energy conservation resulting solely from the improved operation of large energy consuming plant. The work was performed at a major manufacturing plant in the U. K. with an annual energy consumption of the order of 600 gigawatt-hours and an annual energy bill of the order of E10 million.