This paper presents a methodology, which is applied to the meat industry, for the evaluation and assessment of the economical impact of customers participating in operation markets by using the flexibility they may have, as well as the amount of CO2 avoided to be emitted into the atmosphere. The particular market conditions in the Spanish context have been considered. Thus, real prices of operation markets in Spain have been used to evaluate the potential profitability, even if customers are not actually allowed to participate in such markets at the moment. The economic evaluation requires a cost-benefit analysis, as presented in the methodology. The procedure followed evaluates the maximum daily benefit obtained by the customer when offering all its flexibility in operation markets, so that it can make a decision based on the expected benefits. In order to determine the value of this benefit, different aspects are evaluated, including the amount of money saved during the flexibility actions due to the energy not consumed or shifted to cheaper periods, as well as the costs that the customer incurs when a flexibility action is performed. Finally, the obtained results for a typical customer are extrapolated to the whole segment in the country. (C) 2012 Elsevier Ltd. All rights reserved.