The hypothesis is that "a system optimisation model can be a powerful tool to produce basic data for strategic decision making in a local energy company". Another question is: do the companies trust the results? The model used is MODEST, which is a model for energy-system optimisation, built on linear programming. The local energy system in the municipality of Borlänge, has been analysed by means of MODEST and at the same time a traditional study has been carried out by an experienced energy-consultant. Both investigations were made under exactly the same conditions but totally independent of each other. Both studies came to same conclusions, and this was very important for the continued work.

A more extensive investigation was made when five communities, including Borlänge, joined to analyse the optimal energy supply in the region of Dalarna. The other communities are Hedemora, Säter, Avesta and Falun. By following the decision-making process in Borlänge and the other communities it has been possible to judge the usefulness of the MODEST mode! and the concept of energy system analyses that goes with it. The energy companies were interviewed about their experiences of the model. They all agree that they have confidence in the model, as the results correspond with their own calculations and knowledge of their energy systems. The process is easy to follow and the inputs to the model are data that always have to be processed in an investigation of a new investment or other changes of the energy supply. The result of the analysis is easy to comprehend.

Regarding Borlänge a decisive strategic decision has not yet been made. That depends on external insecurities on the energy market which are outside the modelling process. Not making a decision is also a strategic act. Based on the results of the analysis that have been made during the period of this work, 1997-1999, Borlänge Energy has decided to postpone the final decision for two or three years. The president of Borlänge Energy, Anders Lindberg, says that when it is time to make a strategic decision they will use the model again. The other energy companies also agree that their future decisions will be built on the results of the MODEST-analyses.

The conclusions of the thesis state that the system-analyses model MODEST calculates correctly and the concept of the analysing process is well adapted to a local energy system. The systematic way in which the analysing process is carried out stimulates the creativity and creates an active learning process among the participants. The results are trustworthy.