To realise the potential of renewable energy to reduce greenhouse gas emissions, it is recognised that flexible energy storage is required; ideally for long periods of time, even seasonally. The production of renewable combustible gases such as synthetic methane is an emerging technology that can bridge that gap. Synthetic methane is synthesised by an innovative biomethanation process using hydrogen produced by electrolysis and carbon dioxide from sources such as water treatment, anaerobic digestion and industrial processes. Rapid response electrolysis provides a means of balancing intermittent renewable generation and solving electricity grid frequency problems arising from their increasing use. The UK gas infrastructure has the capacity to store and distribute over three times the energy distributed by the electricity network and represents an underutilised asset for the storage of renewable energy. Synthetic methane production is unique in being able to link the electricity and gas networks as a means of balancing renewable energy production, provide long-term storage of energy, decarbonising the largest source of heat in the UK and improve security of supply.