A chromosome model that simulates the operation patterns of an energy system was introduced into a simple Genetic Algorithm, and a method of dynamic optimization was developed. This paper analyses the operation planning of an energy system that uses in combination a solar power module, proton-exchange membrane fuel cell cogeneration (PEMFC-CGS) with methanol steam reforming, a geo-thermal heat pump, heat storage and battery, commercial power, and a kerosene boiler. The hours of operation of each energy device and the rate of the energy output were calculated by having introduced the analysis program developed by this study. Three objective functions: (a) minimization of operation cost; (b) minimization of the error of demand-and-supply balance; and (c) minimization of the amount of greenhouse gas discharge were given to the optimization analysis of the system. Furthermore, the characteristics of the system operation planning under each objective function are described. Copyright (C) 2007 John Wiley & Sons, Ltd.