The European Union and the United States of America are fostering electrification of road transport as a means for achieving ambitious policy targets set to tackle air pollution and climate change. In 2011, the US DoE Argonne National Laboratory (ANL) and the EC Joint Research Centre (JRC) established a collaborative work programme for pre-normative research on interoperability of smart grids and electric vehicles, as well as fuel/energy efficiency of hybrid- and full-electric vehicles. The present paper reports about a joint experimental campaign on a plug-in range extended vehicle (REEV) carried out at ANL’s Advanced Powertrain Research Facility (APRF) and at JRC’s Vehicle Electric Laboratory (VeLA 8). The vehicle was tested on the two roller benches against EU and US legislative cycles, at representative ambient temperatures varying between -30°C and 50°C, in order to investigate the impact of extreme ambient conditions on fuel and energy efficiency.