Many nations have proposed targets for renewable energy production that can only be described as ambitious, given the current levels and the short time frames involved. Proposals in the United States aim to increase renewable electricity production to 15 percent by 2020, a significant amount, given that hydropower capacity is extremely unlikely to expand. The feasibility of achieving these goals depends importantly on technological innovation that will lower the cost of these non-emitting energy sources. Toward these ends, Organisation for Economic Co-operation and Development (OECD) countries have implemented a wide range of policies to reduce greenhouse gas emissions and stimulate innovation in cleaner technologies.