The fact that market experience improves performance and reduces prices is well known and widely exploited in technology-intensive industries, but sparsely used in analysis for energy technology policy. Knowledge of the "experience effect" can help in the design of efficient programmes for deploying of environment-friendly technologies. The effect must be taken into account when estimating the future costs of achieving targets, including targets for carbon dioxide reduction. This book discusses issues raised by the "experience effect", such as price-cost cycles, competition for learning opportunities in the market, risk of "technology lockout" and the effects of research, development and deployment policies on technology learning. Case studies illustrate how experience curves can be used to set policy targets and to design policy measures that will encourage both investment in and use of environment-friendly energy technologies. Low-cost paths to stabilising CO2 emissions are explored.