The inadequate description of real input costs and the assumption of substitutability inherent in financial analysis of production systems can lead to false conclusions and poor decision making. As an alternative, a number of investigators have turned their attention to the energy costs of production. There are many methods used to evaluate the energy cost of a product, often yielding substantially different results. The purpose of this review is to explain these variations in results, which are often due to the different aims of the investigations.
