The paper describes the results of a survey carried out with leading EU experts on the future costs of batteries for electric and plug-in hybrid vehicles and the uncertainty surrounding them. Battery costs are one of the main components in the overall costs of EVs and improvements could be brought about by increased investments in research, development and demonstration (RD&D). Experts' judgements are collected to shed light on the inherently uncertain relationship between RD&D efforts and the consequent technical progress in batteries. The analysis of the experts data results in a number of important policy recommendations to guide future RD&D choices and target commitments both for the EU and its member states. (C) 2013 Elsevier Ltd. All rights reserved.