Low-grade heat (below 200 °C) is available in vast quantities from industry, or from standard roof-top solar thermal collectors. However, the production of electric power from these heat sources is challenging with existing technologies. Thermally regenerative batteries allow both the conversion and the storage of thermal energy into electric power, but they suffer from low operation voltages and low output power. Here, we propose a thermally regenerative nanoslurry flow battery based on copper complexation with acetonitrile in non-aqueous solutions operating at voltages above 1 V. The Cu(I) complex can be destabilized by the removal of acetonitrile by distillation, leading to the production of solid copper nanoparticles and Cu(II) in solution, thereby charging the battery. We demonstrate the electricity production at average power densities of 90 W m−2 and peak-power densities up to 150 W m−2, and estimate the theoretical efficiency of the full system at 2%. The results demonstrate a proof-of-concept for harvesting and storage of electricity from low-quality heat.