Book excerpt: Renewable Energy - Market and Policy Trends in IEA Countries reviews the experience of IEA countries after the oil crisis in the 1970s initiated a surge of investments in renewables research and development. While use of renewables has grown rapidly, they still account for only a small portion of the IEA energy mix. Hydropower, bioenergy and geothermal energy are mature technologies that contribute about 5 - 6% to primary energy supply. Solar, wind, and other new renewables have experienced rapid technology development, but as yet they represent only a small share.This work examines policies and measures that have been introduced in IEA countries to increase the cost effective deployment of renewables, reviews the objectives behind these policies, and evaluates the results. The aim is to identify best practices in order to assist governments in making future policy decisions.