This paper describes the operation of a bipolar alkaline electrolyser which is at least 60% efficient at evolving a hydrogen/oxygen mix. The electrolyser consists of 12 stainless steel (SS316L) electrodes of area 5400 cm(2) in a sealed polypropylene unit. A pulsed potential waveform is applied to the electrodes in 0.12 M KOH electrolyte yielding on the order of 320 dm(3)/kWh of the hydrogen/oxygen mix. This compares favourably with commercial devices that are designed to yield hydrogen alone. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.