A hurdle to the commercialization of thermoelectrochemical cells (TECs) based on the redox reaction of hexacyanoferrate (HCF) to convert low-grade waste heat into electricity is the high manufacturing cost resulting from the noble electrode materials like Pt and nanostructured carbon. Herein, we report the successful exploitation of low-cost Cu, which has not been considered ever for the TEC electrode material because of its heavy corrosion in the operating condition. Interestingly, we found that by precisely tuning the pH of the electrolyte-containing HCF to the immunity window, Cu was applicable to a TEC electrode, showing a performance closely equal to Pt and superior to carbon materials with negligible corrosion. Cu-based TECs can achieve a commercially viable module cost of $0.19 W^–1, which far exceeds the general cost target for thermoelectric devices (∼$1 W^–1) and is even more competitive than that for commercial solar power (∼$0.4 W^–1).