Energy Financing Districts (Property Assessed Clean Energy, Sustainable Energy Financing, Clean Energy Assessment Districts, Contractual Assessments, or Special Tax Districts) were first proposed by the City of Berkeley, California in 2007 and have received increasing attention as a mechanism for financing residential or commercial clean energy projects, including energy efficiency, solar photovoltaic, or solar thermal systems. EFDs represent one specific and powerful example of an intellectual innovation that is broadly applicable to fostering a profitable transition to a clean energy economy at the local, regional, national, and global levels.