Alkaline water electrolysis is considered to be a basic technique for hydrogen production. Many researchers have investigated the water electrolysis in order to promote electrochemical reaction. The effects of voltage, solution concentration, and space between the pair of electrodes on the amount of hydrogen produced and consequently on the overall electrolysis efficiency are experimentally investigated. The alkaline water electrolysis of different potassium hydroxide aqueous solutions is conducted under atmospheric pressure using stainless steel electrodes. The experimental results showed that, the performance of alkaline water electrolysis unit is highly affected by the voltage input and the gap between the electrodes. Higher rates of produced hydrogen can be obtained at smaller space between the electrodes and also at higher voltage input. Higher system efficiency was also gained at smaller gap distances between the pair of electrodes.