Hydrogen has the potential to transform the UK energy system - away from its present state of fossil-fuel dependence towards a cleaner low-carbon future. In abstract, it is possible to imagine a new hydrogen energy economy in which hydrogen is generated, transported, stored and made available for use in homes, businesses and for transport. However, despite the hyperbole about the potential for hydrogen and its desirability , this hydrogen energy economy is not inevitable. The gap between where we are now and this abstract future is substantial. Furthermore, the transition path to an energy system with hydrogen at its core is fraught with uncertainty. The purpose of this short working paper is to stimulate thinking and debate about possible transition paths to hydrogen use on a large scale, and the likelihood that this transition will actually happen. It begins by setting out some key messages for hydrogen from a number of recent scenario exercises that have focused on the future of energy systems to 2050. The paper then proceeds to analyse some existing work on the nature of large technical systems such as the electricity supply industry, and the way in which they are financed and developed. The paper concludes with some pointers for policy makers and firms wishing to facilitate and implement the transition to a less carbon-intensive energy system.