Efficient energy usage, sometimes simply called energy efficiency, is the goal of efforts to reduce the amount of energy within industries. More energy-efficient industries could reduce the problems of pollution, global warming, energy security, and fossil fuel depletion. Many chemicals are produced under high-pressure and at high temperatures and later the product cleaned under lower pressure and temperature, this energy could be exploited for electricity cogeneration using an open gas turbine within an exothermic reactor circuit system. In the presented work, an NLP model is formulated as an optimum energy target of process integration, steam production within an exothermic reactor, and electricity generation using an open gas turbine, into an exothermic reactor circuit system. This simultaneous NLP approach can accurately account for capital cost, the integration of combined heat and power, process modification, and additional production tradeoffs, and can thus yield a better solution. This approach is illustrated using an existing, complex methanol production process as different total-efficiency for electricity cogeneration. The objective function generates a possible increase in annual profit of 1.0 MEUR/a with 50% efficiency and 1.79 MEUR/a with 60% efficiency. (C) 2013 Elsevier Ltd. All rights reserved.