Aluminum-water reaction is known as a candidate for production of hydrogen. Ball milling is used to activate Al powder to react with water. In spite of numerous studies of effect of ball milling, not enough attention has been paid to the fact that the high energy ball milling is an energy consuming process that can markedly adds to the final price of produced hydrogen by this method. This research is an attempt to establish optimum milling parameters and steady state time for high energy ball milling of Al powder; the prolonged milling after that time does not have any effect on the particle size and activation of Al powder, but consumes additional energy and introduces impurities to milled powder. We use different criteria to define steady state milling time; morphology of Al powder, particle size, presence of imperfection in the microstructure and preferred orientation of Al grains. Finally the milled powders for different times were used to react with water. Based on the amount of produced hydrogen and changes in microstructure, the best milling time is proposed to reduce the energy consumption for Al powder activation and increase hydrogen production.