This paper investigates the viability of using hydrogen energy storage to supplement renewable energy when used to meet a significant and fundamental human need, in this case, large-scale drinking water supplies for around 50,000 people in Newhaven, in South East England, and in Massawa in Eritrea. Modelling was conducted to derive the amount of water that various reverse osmosis plants would deliver from various combinations and amounts of renewable power and hydrogen storage input, at varying feedwater temperatures. Analysis was then conducted to assess the cost effectiveness of using renewable energy with hydrogen storage in comparison to using renewable power without energy storage to power the reverse osmosis plant. The cost of the hydrogen storage scenarios were compared with the costs associated with the equivalent conventionally powered scenario: Coal fired plant with carbon capture and storage (CCS) at Newhaven. Diesel generator at Massawa. This comparison was made with and without the external costs associated with conventional energy production and use. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.