Combined Heat and Power (CHP) plants are increasingly used, when feasible, as a mean to reduce fuel consumption and CO2 emissions. The thermal and electrical production must be adapted to load requirements and must lead to the fulfilment of all the constraints imposed by energy saving regulations. As one of such requirements [a minimum "fuel energy savings ratio" (FESR)] is an integral constraint that can be evaluated only at the end of each year of production, during the design phase of the plant it is of the utmost importance to have a fast algorithm able to simulate and optimize the operating conditions of all the candidate CHPs configurations, as the non-compliance with FESR regulations may lead to loose significant tax discounts, and therefore make the investment less profitable. The paper describes a suitable algorithm and its application to the optimization of a real CHP site located in Italy; besides, this work has led, as a further step toward the optimized control of larger systems, to the introduction of an additional degree of freedom ("on-off" state of some machines) extending in principle the optimization procedure to multinode CHP plants. (C) 2010 Elsevier Ltd. All rights reserved.