A power-to-water (P2W) battery includes, a thermal energy storage (TES) unit made of high-storage-density media for storing heat, a hygroscopic solution container including an inner container for receiving the TES unit therein, a water vapor permeable membrane disposed outside and around the inner container thereby forming a space therebetween, first and second sealing members for sealing the space, and a hygroscopic solution disposed in the sealed space, and a condenser disposed downstream to the hygroscopic solution container and coupled thereto, wherein the hygroscopic solution is capable of absorbing the atmospheric water vapor, which is released by the heat stored within the TES unit when the TES unit is received in the inner container, and the atmospheric water vapor released from the hygroscopic solution is condensed into the water by the condenser.