This work treats recommendations based on energy systems engineering. The focus is on what can be learned by different methods about the roles that demand-side energy efficiency should play in the energy system. In the first part of the thesis, two case studies of local energy planning demonstrate the role of demand-side energy efficiency: energy systems engineering suggests a design in which energy efficiency improvements are aligned with the whole technical energy system. One result of the case studies is that the energy consumers invest in fewer energy efficiency measures than recommended by the methodologies applied. This indicates that there are important aspects of demand-side energy efficiency that are ignored by the methodologies used. In this work, the cause of the difference between the recommended and observed investments is addressed by an investigation of the customer's transaction cost for the energy efficiency investment. The second part is an application of the viable system model and focuses on the role of energy efficiency activities at a public energy utility. A case study demonstrates that most energy efficiency activities were run to support energy sales and, hence, were totally entwined with the traditional business. This role observed is compared with that suggested by the demand-side management methodology. The comparison shows that demand-side management is not capable of handling important aspects of interrelations between energy efficiency activities and energy sales. The work provides a language for further discussion of the role of energy efficiency activities at energy utilities.