Using a global systemic approach, the wind energy system operation behaviour is first simulated using five different types of power curve for the wind turbine. Adding physical (charge current limitation) and cost considerations, we have determined the optimized energy system for various levels of satisfaction (LLP), i.e. both able to satisfy the load with a certain percentage of the load not satisfied and to offer the lowest kWh cost. We studied the influences of the power profile of the wind turbine that affect productivity and the relative repartition between input power and output power and wasted energy. This wasted energy decreases rapidly with the value of the LLP. Copyright (C) 2001 John Wiley & Sons, Ltd.