At around the same time, Tiwari et al. reported a comparison between a 'bubble-free' cell employing Gortex gas diffusion electrodes and conventional, bubble-generating electrolysis cells. They calculated that the contribution of bubble formation to the activation overpotential was ~0. 16 V at 80 o C, excluding the effect of impedance. The energy efficiency decrease caused by bubble formation in conventional, bubble-generating electrolysers was estimated to be ≥11.9% (vs. the Lower Heating Value, LHV, of hydrogen).