This report is the product of a workshop held in August 2012 in Boulder, Colorado, for more than 90 leading technical and industry experts in the smart grid community. The workshop was a collaborative effort of NIST and the Renewable and Sustainable Energy Institute (RASEI), a joint institute of the University of Colorado Boulder and the National Renewable Energy Laboratory (NREL). The document reflect the near-consensus opinions of the attendees, and are intended to be of particular value to industry. It summarizes the major impediments to smart grid development and deployment that were discussed during the August workshop. It indicates the participants’ prioritization of technological and measurement science challenges, as well as a number of non-technical challenges.