Converting low-grade waste heat into electrical energy helps alleviate the increasingly tense energy crisis. Here, we present a feasible approach for low-grade waste heat recovery, called bimetallic thermally-regenerative ammonia-based flow battery (B-TRAFB), realizing high-voltage discharge and low-voltage charge at the same temperature. The performance of a cost-effective and structure-compact copper/zinc bimetallic thermally-regenerative ammonia-based battery (Cu/Zn-TRAFB) is investigated comprehensively. A peak power density of ∼280 W m−2 is achieved by a single Cu/Zn-TRAFB cell, and with this case, the net energy density is about 1280 Wh manolyte −3 with a thermoelectric conversion efficiency of 0.34% (2.7% of the Carnot efficiency). The power density obtained herein is much higher than those previously reported for ammonia-based batteries and other liquid-based heat-to-electricity technologies. The cell voltages, currents and power densities can be boosted by adding stacked cells in series or parallel. The energy conversion efficiency can be promoted to 1.64% (27% of the Carnot efficiency) by optimizing the thermal regeneration process.