The paper analyzes the links among energy, economy, and the natural environment. This matter requires the reconsideration of energy efficient and low emission technologies and the definition of new instruments for the analysis of energy systems as well as for the definition of energy policies. After an overview of the methods available in the literature, dealing with a multidimensional analysis of energy system, the authors propose a quantitative approach based on the use of two different thermodynamic based utility functions. The utilization of those functions permits to join thermodynamic and environmental performance of the energy system, to analyze the effects of their interaction and to obtain a more logical comparison among different energy systems, accepting the multidimensional nature of the problem but maintaining a system analysis in the way engineers are accustomed to. Two cases are discussed and analyzed.