Herein, we clarify the role of electrochemistry and surface chemistry in the water-induced electricity generation from electrically conductive solids. A series of WIEGs is fabricated with CBNP-coated membrane and different current collectors. Results show that the generated electricity depends on the configuration of the device, the electrochemical activity of current collectors, the surface chemistry of CBNP, as well as the ion concentration and the pH value of water. It is found that the main driving force for these WIEGs is the electrochemical reactions between the pair of electrically conductive solids in water. Particularly, it is proved that oxygen also contributes to the output performance of the WIEGs via participating in the electrochemical reactions. Based on the clarified mechanisms, we further designed a hydrogel-based portable WIEG that can produce stable voltage for over one month without the addition of extra water, showing its great potential in practical applications. This work not only illuminates the complicated mechanisms involved in the water-induced electricity generation technology but also demonstrates its potential for continuously powering a wide range of applications.