Large scale deployment of intermittent renewable energy induces new challenges for energy systems. They have to balance the volatile energy consumption with the variable power generation. Thus all other components of a renewable energy system are required to be more flexible than they are at present. Storing surplus energy to meet demands when required is one technical solution of balancing this demand. This study analyses the economic performance of an innovative storage technology, known as stored energy in the sea (StEnSea), and compares the findings of the economic analysis with the costs of alternative storage technology options, namely compressed air energy storage (CAES) and pumped hydro storage (PHES) plants, which are comparable in capacity and their balancing performances. Results have shown that the required price arbitrage for the economic operation of the StEnSea technology at a storage farm with 80 storage units and 400 MW ranges from 4 (sic)ct kWh-1 to 20 (sic)ct kWh-1 and strongly depends on the annual operation cycles. The comparison of costs for storing surplus electricity providing power during demand periods when using the StEnSea technology with the costs of CAES and PHES for equivalent services have shown that the StEnSea technology is cost competitive. (c) 2017 Published by Elsevier Ltd.