Water electrolysis linked to intermittent renewable power can produce economical green hydrogen only when it has high load flexibility and fast response time. Therefore, fast mass and ion transport as well as electrode kinetics are required to propel these electrochemical transformations at useful rates. Among the effects of overvoltage on the dynamic characteristics, little is known about the influence of the diaphragm film on the dynamic characteristics of alkaline water electrolysis. Here, we present the effect of the diaphragm membrane on the dynamic behavior of alkaline water electrolysis. Cells equipped with various membranes were tested under rapid load changes to determine the kinetics according to the JRC protocol. The low-resistance membrane clearly showed the fastest response time from the minimum power to the maximum power dynamics test protocol, which was superior to that of the Zirfon membrane, a commercial separator. In addition, we evaluated the responsiveness of water electrolysis to estimate various grid services, and the low ohmic resistance of the membrane was related to the fast response time. This study proposes that the low ohmic resistance of the alkaline electrolyte membrane is one of the key figures of merit for grid balancing service and dynamic performance.