Abstract A literature survey indicates that decisions about whether to reject or accept an investment are largely based on financial factors. The survey also indicates that a comparison of different efficiency improvement studies is difficult because their results are not readily commensurable. From the management perspective, more information on the physical aspects affecting efficiency is needed. From the engineering perspective, studies on integrated processes deal with a number of criteria that are often in conflict with each other, and for which information is difficult to produce. This paper discusses ways to analyse efficiency improvement studies in integrated industrial processes. The paper demonstrates how these analyses could be made more comprehensive. The paper presents a case study where test runs and simulations were carried out to improve process efficiency by adjusting process operating parameters. The case study was re-evaluated using a novel approach that has been developed to assess the efficiency of integrated systems. This includes considerations from three design perspectives: energy efficiency, material efficiency and operational efficiency, which, when analysed simultaneously, result in a more complete set of design and evaluation criteria.