Current simulation tools used to analyze, design and size wind-hydrogen hybrid systems, have several common characteristics: all use manufacturer wind turbine power curve (obtained from UNE 61400-12) and always consider electrolyzer operating in nominal conditions (not taking into account the influence of thermal inertia and operating temperature in hydrogen production). This article analyzes the influence of these parameters. To do this, a mathematical wind turbine model, that represents the manufacturer power curve to the real behaviour of the equipment in a location, and a dynamic electrolyzer model are developed and validated. Additionally, hydrogen production in a wind-hydrogen system operating in "wind-balance" mode (adjusting electricity production and demand at every time step) is analyzed. Considering the input data used, it is demonstrated that current simulation tools present significant errors in calculations. When using the manufacturer wind turbine power curve: the electric energy produced by the wind turbine, and the annual hydrogen production in a wind-hydrogen system are overestimated by 25% and 33.6%, respectively, when they are compared with simulation results using mathematical models that better represent the real behaviour of the equipments. Besides, considering electrolyzer operating temperature constant and equal to nominal, hydrogen production is overestimated by 3%, when compared with the hydrogen production using a dynamic electrolyzer model. (C) 2010 Elsevier B.V. All rights reserved.