A bilayer polymer-based moisture-electric generator (MEG) is developed for self-sustaining and efficient energy harvesting from the hydrological cycle. The device consists of a hydrophobic porous poly(vinylidene fluoride-co-hexafluoropropene) (P(VdF-HFP)) layer and a hygroscopic ionic hydrogel layer (PP/IH). The hydrophobic layer enables radiative cooling, reducing daytime evaporation and enhancing nighttime moisture sorption. The ionic hydrogel, containing LiCl and phytic acid, improves moisture sorption and ion transport, enabling efficient energy conversion. The device generates a voltage of ~0.88 V and a current of ~306 μA, with a maximum power density of ~51 μW cm⁻² at 25 °C and 70% RH. It operates continuously for 6 days in outdoor conditions. The radiative cooling effect of the P(VdF-HFP) layer maintains a stable hydrological cycle, ensuring continuous water/ion flow. The ionic hydrogel's structure and composition enhance moisture sorption and ion transport, leading to sustained power output. The device demonstrates excellent environmental adaptability, functioning in a wide temperature range from -20 °C to 50 °C. The PP/IH outperforms other MEGs in terms of electrical output, with a maximum open-circuit voltage of 0.88 V and short-circuit current of 306 μA cm⁻². The device's performance is validated through various tests, including electrical output under different humidity and temperature conditions, and its scalability is demonstrated by connecting multiple units in series and parallel. The PP/IH shows potential for applications in building energy conservation and self-powered wearable devices. The study provides insights into improving moisture-electric generation in hot and dry regions and advancing eco-friendly energy systems.A bilayer polymer-based moisture-electric generator (MEG) is developed for self-sustaining and efficient energy harvesting from the hydrological cycle. The device consists of a hydrophobic porous poly(vinylidene fluoride-co-hexafluoropropene) (P(VdF-HFP)) layer and a hygroscopic ionic hydrogel layer (PP/IH). The hydrophobic layer enables radiative cooling, reducing daytime evaporation and enhancing nighttime moisture sorption. The ionic hydrogel, containing LiCl and phytic acid, improves moisture sorption and ion transport, enabling efficient energy conversion. The device generates a voltage of ~0.88 V and a current of ~306 μA, with a maximum power density of ~51 μW cm⁻² at 25 °C and 70% RH. It operates continuously for 6 days in outdoor conditions. The radiative cooling effect of the P(VdF-HFP) layer maintains a stable hydrological cycle, ensuring continuous water/ion flow. The ionic hydrogel's structure and composition enhance moisture sorption and ion transport, leading to sustained power output. The device demonstrates excellent environmental adaptability, functioning in a wide temperature range from -20 °C to 50 °C. The PP/IH outperforms other MEGs in terms of electrical output, with a maximum open-circuit voltage of 0.88 V and short-circuit current of 306 μA cm⁻². The device's performance is validated through various tests, including electrical output under different humidity and temperature conditions, and its scalability is demonstrated by connecting multiple units in series and parallel. The PP/IH shows potential for applications in building energy conservation and self-powered wearable devices. The study provides insights into improving moisture-electric generation in hot and dry regions and advancing eco-friendly energy systems.