Direct conversion of moisture into electricity is emerging as a promising contributor to renewable energy. Having practical utility on sight, we report the development of a robust moisture electric generator (MEG) by creating tandem heterojunctions of oppositely charged layers of metal oxides and hydroxides. The mechanistic insight and great potential utility of metal oxides-hydroxides-based heterojunctions in MEG were first demonstrated by fabricating a bilayer moisture electric generator (BMEG) of exfoliated two-dimensional (2D) sheets of vanadium pentoxide (VO) and β-nickel hydroxide (Ni(OH)2). In contrast to short electric pulses of typical MEGs, BMEG of VO and Ni(OH)2 provides continuous output power 1.06 µW/cm2 (106 µW/cm3 in terms of volume density) for multiple months. The functionality of inorganic materials-based BMEG survived exposure to extreme temperatures (−195 to +200 °C) and prolonged use. The output voltage of overused (80 days) BMEG could be revived by renewing the connections. The single device output potential of BMEG was drastically improved from ∼600 mV to ∼1.02 V upon the incorporation of additional heterojunctions of Al doped ZnO and NiCo2O4. Among continuous power-delivering MEGs, the tandem MEG (TMEG) displayed one of the best power density. Multiple oxide-hydroxide-based BMEGs were connected to obtain output voltage and current up to 40 V and 45 µA, respectively. The output voltage of BMEG can be further improved by 23 % and 34 % by exposing it to white light and waste heat-driven temperature gradient. The sensitivity of BMEG towards atmospheric water molecules is further utilised as self-powered moisture sensors.