Current trends in energy supply and use are patently unsustainable – economically, environmentally and socially. Without decisive action, energy-related emissions of carbon dioxide (CO2) will more than double by 2050 and increased fossil energy demand will heighten concerns over the security of supplies. We can and must change our current path. However, this will take an energy revolution and low-carbon energy technologies will have a crucial role to play. Energy efficiency, sources of renewable energy, carbon capture and storage (CCS), nuclear power and new transport technologies will all require widespread deployment if we are to achieve reductions in greenhouse gas (GHG) emissions. Every major country and sector of the economy must be involved. The task is urgent if we are to make sure that investment decisions taken now do not saddle us with sub-optimal technologies in the long term.