Decarbonising UK transport by 2050 using renewable electricity is a challenge, but achievable given the enormous renewables potential of the UK. However, the scale of transport electricity demand post-2030 means that renewable electricity will remain a ‘scarce’ commodity and must be used as efficiently as possible. Transport cannot therefore be decarbonised one mode at a time, but instead requires an approach that recognises the greater efficiency of some energy pathways and the limited availability of sustainable biofuels. Priority should be given to direct use of electricity where possible, such as through batteries, while minimising the use of energy carriers like hydrogen and synthetic fuels to sectors where these are unavoidable, like shipping and aviation. There is a clear hierarchy for the use of renewable electricity in transport and encouraging the use of e-diesel in road transport or hydrogen in cars comes with a considerable total energy penalty that risks derailing the entire decarbonisation effort.