In many cases the decentralisation of the markets lead to an increased price of energy due to a higher number of companies created between the producers and consumers. This phenomenon tends to tighten the competition and increases the pressure on all the market actors. Under these circumstances a simple economical analysis is in many cases unsatisfactory since the competitiveness of one producer on an energy market is also influenced by other factors such as: fuels price variation, tariffs applied by transport operators and energy providers, introduction of eco- taxes, etc. The proposed analysis method is based on a comparison between the analysed cogeneration system and different alternative solutions, in terms of end consumer''s prices. The proposed mathematical model allows the evaluation of the state of the analysed cogeneration system, as well as the effect of several rehabilitation methods.