This work presents an integrated hydrogen production system using reverse electrodialysis (RED) and waste heat, termed Heat to H 2 . The driving potential in RED is a concentration difference over alternating anion and cation exchange membranes, where the electrode potential can be used directly for water splitting at the RED electrodes. Low-grade waste heat is used to restore the concentration difference in RED. In this study we investigate two approaches: one water removal process by evaporation and one salt removal process. Salt is precipitated in the thermally driven salt removal, thus introducing the need for a substantial change in solubility with temperature, which KNO 3 fulfils. Experimental data of ion conductivity of K + and no in ion-exchange membranes is obtained. The ion conductivity of KNO 3 in the membranes was compared to NaCl and found to be equal in cation exchange membranes, but significantly lower in anion exchange membranes. The membrane resistance constitutes 98% of the total ohmic resistance using concentrations relevant for the precipitation process, while for the evaporation process, the membrane resistance constitutes over 70% of the total ohmic resistance at 40 ∘ . The modelled hydrogen production per cross-section area from RED using concentrations relevant for the precipitation process is 0.014 ± 0.009 m 3 h n a m e d - c o n t e n t c o l o r t y p e r g b c o n t e n t - t y p e b l a c k - 1 (1.1 ± 0.7 g h n a m e d - c o n t e n t c o l o r t y p e r g b c o n t e n t - t y p e b l a c k - 1 ) at 40 ∘ , while with concentrations relevant for evaporation, the hydrogen production per cross-section area was 0.034 ± 0.016 m 3 h n a m e d - c o n t e n t c o l o r t y p e r g b c o n t e n t - t y p e b l a c k - 1 (2.6 ± 1.3 g h n a m e d - c o n t e n t c o l o r t y p e r g b c o n t e n t - t y p e b l a c k - 1 ). The modelled energy needed per cubic meter of hydrogen produced is 55 ± 22 kWh (700 ± 300 kWh kg n a m e d - c o n t e n t c o l o r t y p e r g b c o n t e n t - t y p e b l a c k - 1 ) for the evaporation process and 8.22 ± 0.05 kWh (104.8 ± 0.6 kWh kg n a m e d - c o n t e n t c o l o r t y p e r g b c o n t e n t - t y p e b l a c k - 1 ) for the precipitation process. Using RED together with the precipitation process has similar energy consumption per volume hydrogen produced compared to