This paper looks at tax incentives for energy efficiency in the context of tax reform. It reviews experience with current and past energy efficiency tax incentives and based on this experience provides some guidelines on the most effective ways to apply limited funds to maximize long-term energy savings. Specific options discussed include medium-term incentives for advanced technologies and practices that can permanently transform markets and repayable tax incentives. The paper also includes an analysis of the costs and savings of 13 specific proposals, ranking them on federal cost per million Btu of energy saved.